Patent Application
20200171501
Micro-objects, such as biological cells, can be processed in microfluidic apparatuses. For example, droplets containing micro-objects or reagents can be moved around and merged within a microfluidic apparatus. Embodiments of the present disclosure are directed to improvements in microfluidic apparatuses that facilitate robust manipulation of droplets, allowing complex chemical and biological reactions to be precisely and reproducibly performed at small scale. The reactions include nucleic acid amplification such as PCR. The reactions can also include a series of steps to obtain nucleic acid from cells and prepare a sequencing library therefrom. Droplets can be moved and merged within a microfluidic apparatus by changing an effective wetting property of an electrowetting surface in the microfluidic apparatus. Such movements can facilitate workflows in which cells are processed to assess various cellular properties, optionally after culturing the cell within the microfluidic apparatus. Present solutions for electrowetting are extremely limited in nature and fail to scale or implement additional functionality. For example, when a microfluidic device having an electrowetting configuration is used for nucleic acid amplification, a proper thermal control system at a broad range of temperatures suitable to prevent temperature overshooting is needed. Consequently, a need exists for improved electrowetting surfaces, stable substrates for microfluidic applications, and integration of additional functionality (e.g., cellular growth and characterization prior to downstream processing made possible by electrowetting), all of which will facilitate additional medical research applications.
In some embodiments, a method of processing biological cells in a microfluidic device having an electrowetting configuration is provided. The method can comprise: disposing a first droplet of aqueous medium upon a droplet actuation surface of the microfluidic device, wherein the first droplet comprises one or more biological cells; merging the first droplet with a second droplet of aqueous medium to form a first combined droplet, wherein the second droplet comprises a cell lysing agent; incubating the first combined droplet upon the droplet actuation surface for a first period of time sufficient to lyse the one or more biological cells; and inactivating the cell lysing agent. In some embodiments, the microfluidic device further comprises a substrate having a dielectric layer and a first electrode configured to be connected to an AC voltage source, and a second electrode configured to be connected to the AC voltage source, wherein the dielectric layer is electrically coupled to the first electrode, wherein the droplet actuation surface comprises a hydrophobic layer covalently bonded to the dielectric layer, and wherein, when the first electrode and the second electrode are connected to opposing terminals of the AC voltage source, the substrate is capable of applying an electrowetting force to aqueous droplets in contact with the droplet actuating surface. The methods can be performed on any of the microfluidic devices disclosed herein. For example, the microfluidic device can include an electrowetting configuration that includes a dielectric layer having an electrical impedance of about 50 kOhms to about 150 kOhms. The dielectric layer can be a single layer or a composite of multiple dielectric sub-layers, with at least the outermost dielectric sub-layer being formed by atomic layer deposition (ALD). In certain embodiments, one or more (e.g., all) internal surfaces of the microfluidic device can include an outer hydrophobic layer comprising self-associating molecules covalently bonded to the dielectric layer. The self-associating molecules can include, for example, a linking group and a surface modifying ligand. The linking group can be, for example, a siloxane group or a phosphonic acid group. The surface modifying ligand can be, for example, a linear alkane group or a linear fluoroalkane group. In some embodiments, the method of processing biological cells is a method of preparing a nucleic acid library.
In some embodiments, a method of processing biological cells in a microfluidic device having an electrowetting configuration is provided. The method can comprise: disposing a first droplet of aqueous medium upon a droplet actuation surface of the microfluidic device, wherein the first droplet comprises one or more biological cells; merging the first droplet with a second droplet of aqueous medium to form a first combined droplet, wherein the second droplet comprises a cell lysing agent; incubating the first combined droplet upon the droplet actuation surface for a first period of time sufficient to lyse the one or more biological cells; and inactivating the cell lysing agent. In some embodiments, the microfluidic device further comprises a substrate having a dielectric layer and a first electrode configured to be connected to an AC voltage source, and a second electrode configured to be connected to the AC voltage source, wherein the dielectric layer is electrically coupled to the first electrode, wherein the droplet actuation surface comprises a hydrophobic layer covalently bonded to the dielectric layer, wherein the hydrophobic layer is a monolayer formed from molecules each comprising a surface modifying ligand and a linking group that links the surface modifying ligand to the surface, each molecule having a structure of:
wherein: is the surface; V is a linker; m is an integer of 9 or greater; and wherein, when the first electrode and the second electrode are connected to opposing terminals of the AC voltage source, the substrate is capable of applying an electrowetting force to aqueous droplets in contact with the droplet actuating surface. In some embodiments, V is —Si(OZ)2W—; W is —O— and connects to the surface; and Z is a bond to an adjacent silicon atom attached to the surface or is a bond to the surface. In some embodiments, m is 15, 17 or 19. In some embodiments, the method further comprises filling the enclosure, or a portion thereof, with a first liquid medium which is immiscible with the first and second droplets, wherein the enclosure is filled with the first liquid medium prior to disposing the first droplet upon the droplet actuation surface, and wherein the first liquid medium comprises an organic liquid having branched carbon backbone. In some embodiments, the organic liquid is a carbonate or a hydrocarbon, such as bis(2-ethylhexyl) carbonate or heptamethylnonane. In some embodiments, the first droplet comprises a surfactant, such as a non-ionic surfactant, e.g., TET surfactant, N-(1,3-bis(Glucopyrano side)propan-2-yl)-3-Butyl-3-Cyclohexylheptanamide (Cy-Tripglu), or a polyethylene oxide-polypropylene oxide (PEO-PPO) block copolymer, optionally wherein the PEO-PPO block copolymer is a poloxamer. In some embodiments, the second droplet comprises a surfactant, such as a non-ionic surfactant having a polar head group of a size greater than 750 daltons. For example, the surfactant in the second droplet can be a polysorbate surfactant having a molecular weight of at least 1000 daltons (e.g., polysorbate 20). The methods can further comprise fragmenting DNA or reverse transcribing RNA from the one or more biological cells, and can further comprise amplifying the resultant fragmented DNA or cDNA. The methods can be performed on any of the microfluidic devices disclosed herein. For example, the microfluidic device can include an electrowetting configuration that includes a dielectric layer having an electrical impedance of about 50 kOhms to about 150 kOhms. The dielectric layer can be a single layer or a composite of multiple dielectric sub-layers, with at least the outermost dielectric sub-layer being formed by atomic layer deposition (ALD). In certain embodiments, one or more (e.g., all) internal surfaces of the microfluidic device can include an outer hydrophobic layer comprising self-associating molecules covalently bonded to the dielectric layer. In some embodiments, the method of processing biological cells is a method of preparing a nucleic acid library.
In some embodiments, a method of processing biological cells in a microfluidic device having an electrowetting configuration is provided. The method can comprise: disposing a first droplet of aqueous medium upon a droplet actuation surface of the microfluidic device, wherein the first droplet comprises one or more biological cells; merging the first droplet with a second droplet of aqueous medium to form a first combined droplet, wherein the second droplet comprises a cell lysing agent; incubating the first combined droplet upon the droplet actuation surface for a first period of time sufficient to lyse the one or more biological cells; and inactivating the cell lysing agent. In some embodiments, the microfluidic device further comprises a substrate having a dielectric layer and a first electrode configured to be connected to an AC voltage source, and a second electrode configured to be connected to the AC voltage source, wherein the dielectric layer is electrically coupled to the first electrode, wherein the droplet actuation surface comprises a hydrophobic layer covalently bonded to the dielectric layer, wherein the hydrophobic layer is a monolayer formed from molecules each comprising a surface modifying ligand and a linking group that links the surface modifying ligand to the surface, each molecule having a structure of:
wherein: is the surface; V is a linker; n+m+j is 13 or greater, n is 5 or greater, and m ranges from 2 to 13, and j is 0 or 1; and wherein, when the first electrode and the second electrode are connected to opposing terminals of the AC voltage source, the substrate is capable of applying an electrowetting force to aqueous droplets in contact with the droplet actuating surface. In some embodiments, V is —Si(OZ)2W—; W is —O— and connects to the surface; and Z is a bond to an adjacent silicon atom attached to the surface or is a bond to the surface. In some embodiments, m is 2, and/or n is 11, 13, or 15. In some embodiments, the first droplet comprises a surfactant, such as a non-ionic surfactant, e.g., TET surfactant, N-(1,3-bis(Glucopyranoside)propan-2-yl)-3-Butyl-3-Cyclohexylheptanamide (Cy-Tripglu), or a polyethylene oxide-polypropylene oxide (PEO-PPO) block copolymer, optionally wherein the PEO-PPO block copolymer is a poloxamer. In some embodiments, the second droplet comprises a surfactant, such as a non-ionic surfactant having a polar head group of a size greater than 750 daltons. For example, the surfactant in the second droplet can be a polysorbate surfactant having a molecular weight of at least 1000 daltons (e.g., polysorbate 20). The methods can further comprise fragmenting DNA or reverse transcribing RNA from the one or more biological cells, and can further comprise amplifying the resultant fragmented DNA or cDNA. The methods can be performed on any of the microfluidic devices disclosed herein. For example, the microfluidic device can include an electrowetting configuration that includes a dielectric layer having an electrical impedance of about 50 kOhms to about 150 kOhms. The dielectric layer can be a single layer or a composite of multiple dielectric sub-layers, with at least the outermost dielectric sub-layer being formed by atomic layer deposition (ALD). In certain embodiments, one or more (e.g., all) internal surfaces of the microfluidic device can include an outer hydrophobic layer comprising self-associating molecules covalently bonded to the dielectric layer. In some embodiments, the method of processing biological cells is a method of preparing a nucleic acid library.
In some embodiments, a method of amplifying nucleic acid in a microfluidic device having an electrowetting configuration is provided. The method can comprise: disposing a first droplet of aqueous medium upon a droplet actuation surface of the microfluidic device, wherein the first droplet comprises nucleic acid; merging the first droplet with a second droplet of aqueous medium to form a combined droplet, wherein the second droplet comprises a nucleic acid polymerase, and wherein the combined droplet comprises a buffer and precursors (e.g., nucleotides, primers, etc.) that support a polymerase activity of the nucleic acid polymerase; and incubating the combined droplet upon the droplet actuation surface, under conditions that promote amplification of the nucleic acid originating from the first droplet. In some embodiments, the microfluidic device further comprises a substrate having a dielectric layer and a first electrode configured to be connected to an AC voltage source, and a second electrode configured to be connected to the AC voltage source, wherein the dielectric layer is electrically coupled to the first electrode, wherein the droplet actuation surface comprises a hydrophobic layer covalently bonded to the dielectric layer, and wherein, when the first electrode and the second electrode are connected to opposing terminals of the AC voltage source, the substrate is capable of applying an electrowetting force to aqueous droplets in contact with the droplet actuating surface. In some embodiments, incubating the combined droplet under conditions that promote amplification comprises adjusting the temperature of the microfluidic device to a first temperature that is sufficient to cause the nucleic acid originating from the first droplet to denature partially or fully. In some embodiments, incubating the combined droplet under conditions that promote amplification further comprises adjusting the temperature of the microfluidic device to a second temperature that promotes priming of the nucleic acid originating from the first droplet and/or the template-based extension of the primed nucleic acid. In some embodiments, the first droplet comprises a surfactant, such as a non-ionic surfactant, e.g., TET surfactant, N-(1,3-bis(Glucopyranoside)propan-2-yl)-3-Butyl-3-Cyclohexylheptanamide (Cy-Tripglu), or a polyethylene oxide-polypropylene oxide (PEO-PPO) block copolymer, optionally wherein the PEO-PPO block copolymer is a poloxamer. In some embodiments, the second droplet comprises a surfactant, such as a non-ionic surfactant, e.g., a polysorbate surfactant having a molecular weight of at least 1000 daltons, optionally polysorbate 20, or a polyethylene oxide-polypropylene oxide (PEO-PPO) block copolymer, optionally a poloxamer. The methods can be performed on any of the microfluidic devices disclosed herein. For example, the microfluidic device can include an electrowetting configuration that includes a dielectric layer having an electrical impedance of about 50 kOhms to about 150 kOhms. The dielectric layer can be a single layer or a composite of multiple dielectric sub-layers, with at least the outermost dielectric sub-layer being formed by atomic layer deposition (ALD). In certain embodiments, one or more (e.g., all) internal surfaces of the microfluidic device can include an outer hydrophobic layer comprising self-associating molecules covalently bonded to the dielectric layer. The self-associating molecules can include, for example, a linking group and a surface modifying ligand. The linking group can be, for example, a siloxane group or a phosphonic acid group. The surface modifying ligand can be, for example, a linear alkane group or a linear fluoroalkane group.
In some embodiments, a system for operating a microfluidic device is provided. The system can comprise: a support configured to hold and operatively couple with a micro fluidic device, the support comprising an electrical signal generation subsystem configured to selectively apply a biasing voltage across a pair of electrodes in the microfluidic device when the microfluidic device is held by, and operatively coupled with, the support; a thermal control subsystem configured to regulate a temperature of the microfluidic device when the microfluidic device is held by, and operably coupled with, the support, the thermal control subsystem comprising a thermal control circuit, a thermistor, and a Peltier thermoelectric device, wherein the thermistor is positioned in the support and configured to measure the temperature of a location at or proximal to a surface of the microfluidic device, wherein the Peltier thermoelectric device is configured to interface with the surface of the microfluidic device, and wherein the thermal control circuit is configured to follow rules correlating a temperature value measured by the thermistor with a target temperature and a power output of Peltier thermoelectric device. In certain embodiments, the rules comprise: setting the power output of the Peltier thermoelectric device to a first value if the difference between the target temperature and the thermistor-measured temperature is larger than N; setting the power output of the Peltier thermoelectric device to a second value lower than the first value if the difference between the target temperature and the thermistor-measured temperature is equal to or smaller than N and larger than M; and determining the power output of the Peltier thermoelectric device by a proportionate-integral-derivative (PID) loop controller with the thermistor-measured temperature as an input if the difference between the target temperature and the thermistor-measured temperature is smaller than or equal to M. In certain embodiments, M is in the range of 5° C. to 15° C. (e.g., about 7° C. to about 13° C., or about 8° C. to about 12° C., or about 9° C. to about 11° C.) and N is in the range of 1° C. to 5° C. (e.g., about 2° C. to about 4° C. or about 2.5° C. to about 3.5° C.). In some embodiments, the first value is in the range of 70% to 100% power output of the Peltier thermoelectric device. In some embodiments, the second value is a power output value determined from calibration data correlating a plurality of target temperature values with a plurality of power output values, optionally wherein: the target temperature values correlated to the power output values were determined by equilibrating a calibration chip comprising a thermocouple with the Peltier thermoelectric device at each of the power output values and associating the temperature registered by the thermocouple following equilibration with the power output value; and/or the plurality of target temperature values comprises at least 4, 5, 6, 7, 8, 9, or 10 values in the range of 0° C. to 100° C., optionally wherein a power output value corresponding to a target temperature value between values represented in the calibration data is determined by linear interpolation. The microfluidic device can be any of the microfluidic devices disclosed herein.
Additional aspects and embodiments of the invention will be evident from the drawings and the detailed description that follows.
This specification describes exemplary embodiments and applications of the disclosure. The disclosure, however, is not limited to these exemplary embodiments and applications or to the manner in which the exemplary embodiments and applications operate or are described herein. Moreover, the figures may show simplified or partial views, and the dimensions of elements in the figures may be exaggerated or otherwise not in proportion. Section headings are provided for the convenience of the reader and do not limit the scope of the disclosure.
As the terms “on,” “attached to,” “connected to,” “coupled to,” or similar words are used herein, one element (e.g., a material, a layer, a substrate, etc.) can be “on,” “attached to,” “connected to,” or “coupled to” another element regardless of whether the one element is directly on, attached to, connected to, or coupled to the other element or there are one or more intervening elements between the one element and the other element. Also, unless the context dictates otherwise, directions (e.g., above, below, top, bottom, side, up, down, under, over, upper, lower, horizontal, vertical, “x,” “y,” “z,” etc.), if provided, are relative and provided solely by way of example and for ease of illustration and discussion and not by way of limitation. In addition, where reference is made to a list of elements (e.g., elements a, b, c), such reference is intended to include any one of the listed elements by itself, any combination of less than all of the listed elements, and/or a combination of all of the listed elements. Section divisions in the specification are for ease of review only and do not limit any combination of elements discussed.
As used herein, “substantially” means sufficient to work for the intended purpose. The term “substantially” thus allows for minor, insignificant variations from an absolute or perfect state, dimension, measurement, result, or the like such as would be expected by a person of ordinary skill in the field but that do not appreciably affect overall performance. When used with respect to numerical values or parameters or characteristics that can be expressed as numerical values, “substantially” means within ten percent.
The term “ones” means more than one.
As used herein, the term “plurality” can be 2, 3, 4, 5, 6, 7, 8, 9, 10, or more.
As used herein, the term “disposed” encompasses within its meaning “located.”
As used herein, a “microfluidic device” or “microfluidic apparatus” is a device that includes one or more discrete microfluidic circuits configured to hold a fluid, each microfluidic circuit comprised of fluidically interconnected circuit elements, including but not limited to region(s), flow region(s), channel(s), chamber(s), and/or pen(s), and (for microfluidic device that include a cover) at least two ports configured to allow the fluid (and, optionally, micro-objects suspended in the fluid) to flow into and/or out of the microfluidic device. Typically, a microfluidic circuit of a microfluidic device will include at least one microfluidic channel and at least one chamber, and will hold a volume of fluid of less than about 1 mL, e.g., less than about 750, 500, 250, 200, 150, 100, 75, 50, 25, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, or 2 μL. In certain embodiments, the microfluidic circuit holds about 1-2, 1-3, 1-4, 1-5, 2-5, 2-8, 2-10, 2-12, 2-15, 2-20, 5-20, 5-30, 5-40, 5-50, 10-50, 10-75, 10-100, 20-100, 20-150, 20-200, 50-200, 50-250, or 50-300 μL.
As used herein, a “nanofluidic device” or “nanofluidic apparatus” is a type of microfluidic device having a microfluidic circuit that contains at least one circuit element configured to hold a volume of fluid of less than about 1 μL, e.g., less than about 750, 500, 250, 200, 150, 100, 75, 50, 25, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 nL or less. A nanofluidic device may comprise a plurality of circuit elements (e.g., at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 50, 75, 100, 150, 200, 250, 300, 400, 500, 600, 700, 800, 900, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000, 6000, 7000, 8000, 9000, 10,000, or more). In certain embodiments, one or more (e.g., all) of the at least one circuit elements is configured to hold a volume of fluid of about 100 pL to 1 nL, 100 pL to 2 nL, 100 pL to 5 nL, 250 pL to 2 nL, 250 pL to 5 nL, 250 pL to 10 nL, 500 pL to 5 nL, 500 pL to 10 nL, 500 pL to 15 nL, 750 pL to 10 nL, 750 pL to 15 nL, 750 pL to 20 nL, 1 to 10 nL, 1 to 15 nL, 1 to 20 nL, 1 to 25 nL, or 1 to 50 nL. In other embodiments, one or more (e.g., all) of the at least one circuit elements is configured to hold a volume of fluid of about 20 nL to 200 nL, 100 to 200 nL, 100 to 300 nL, 100 to 400 nL, 100 to 500 nL, 200 to 300 nL, 200 to 400 nL, 200 to 500 nL, 200 to 600 nL, 200 to 700 nL, 250 to 400 nL, 250 to 500 nL, 250 to 600 nL, or 250 to 750 nL.
A “microfluidic channel” or “flow channel” as used herein refers to a flow region of a microfluidic device having a length that is significantly longer than both the horizontal and vertical dimensions. For example, the flow channel can be at least 5 times the length of either the horizontal or vertical dimension, e.g., at least 10 times the length, at least 25 times the length, at least 100 times the length, at least 200 times the length, at least 500 times the length, at least 1,000 times the length, at least 5,000 times the length, or longer. In some embodiments, the length of a flow channel is in the range of from about 50,000 microns to about 500,000 microns, including any range therebetween. In some embodiments, the horizontal dimension is in the range of from about 100 microns to about 1000 microns (e.g., about 150 to about 500 microns) and the vertical dimension is in the range of from about 25 microns to about 200 microns, e.g., from about 40 to about 150 microns. It is noted that a flow channel may have a variety of different spatial configurations in a microfluidic device, and thus is not restricted to a perfectly linear element. For example, a flow channel may include one or more sections having any of the following configurations: curve, bend, spiral, incline, decline, fork (e.g., multiple different flow paths), and any combination thereof. In addition, a flow channel may have different cross-sectional areas along its path, widening and constricting to provide a desired fluid flow therein.
As used herein, the term “obstruction” refers generally to a bump or similar type of structure that is sufficiently large so as to partially (but not completely) impede movement of target micro-objects between two different regions or circuit elements in a microfluidic device. The two different regions/circuit elements can be, for example, a microfluidic sequestration pen and a microfluidic channel, or a connection region and an isolation region of a microfluidic sequestration pen.
As used herein, the term “constriction” refers generally to a narrowing of a width of a circuit element (or an interface between two circuit elements) in a microfluidic device. The constriction can be located, for example, at the interface between a microfluidic sequestration pen and a microfluidic channel, or at the interface between an isolation region and a connection region of a microfluidic sequestration pen.
As used herein, the term “transparent” refers to a material which allows visible light to pass through without substantially altering the light as is passes through.
As used herein, the term “micro-object” refers generally to any microscopic object that may be isolated and collected in accordance with the present disclosure. Non-limiting examples of micro-objects include: inanimate micro-objects such as microparticles; microbeads (e.g., polystyrene beads, Luminex™ beads, or the like); magnetic beads; microrods; microwires; quantum dots, and the like; biological micro-objects such as cells (e.g., embryos, oocytes, ova, sperm cells, cells dissociated from a tissue, eukaryotic cells, protist cells, animal cells, mammalian cells, human cells, immunological cells, hybridomas, cultured cells, cells from a cell line, cancer cells, infected cells, transfected and/or transformed cells, reporter cells, prokaryotic cells, and the like); biological organelles; vesicles, or complexes; synthetic vesicles; liposomes (e.g., synthetic or derived from membrane preparations); lipid nanorafts (as described in Ritchie et al. (2009) “Reconstitution of Membrane Proteins in Phospholipid Bilayer Nanodiscs,” Methods Enzymol., 464:211-231), and the like; or a combination of inanimate micro-objects and biological micro-objects (e.g., microbeads attached to cells, liposome-coated micro-beads, liposome-coated magnetic beads, or the like). Beads may further have other moieties/molecules covalently or non-covalently attached, such as fluorescent labels, proteins, small molecule signaling moieties, antigens, or chemical/biological species capable of use in an assay.
As used herein, the term “maintaining (a) cell(s)” refers to providing an environment comprising both fluidic and gaseous components and, optionally a surface, that provides the conditions necessary to keep the cells viable and/or expanding.
A “component” of a fluidic medium is any chemical or biochemical molecule present in the medium, including solvent molecules, ions, small molecules, antibiotics, nucleotides and nucleosides, nucleic acids, amino acids, peptides, proteins, sugars, carbohydrates, lipids, fatty acids, cholesterol, metabolites, or the like.
As used herein in reference to a fluidic medium, “diffuse” and “diffusion” refer to thermodynamic movement of a component of the fluidic medium down a concentration gradient.
The phrase “flow of a medium” means bulk movement of a fluidic medium primarily due to any mechanism other than diffusion. For example, flow of a medium can involve movement of the fluidic medium from one point to another point due to a pressure differential between the points. Such flow can include a continuous, pulsed, periodic, random, intermittent, or reciprocating flow of the liquid, or any combination thereof. When one fluidic medium flows into another fluidic medium, turbulence and mixing of the media can result.
The phrase “substantially no flow” refers to a rate of flow of a fluidic medium that, averaged over time, is less than the rate of diffusion of components of a material (e.g., an analyte of interest) into or within the fluidic medium. The rate of diffusion of components of such a material can depend on, for example, temperature, the size of the components, and the strength of interactions between the components and the fluidic medium.
As used herein in reference to different regions within a microfluidic device, the phrase “fluidically connected” means that, when the different regions are substantially filled with fluid, such as fluidic media, the fluid in each of the regions is connected so as to form a single body of fluid. This does not mean that the fluids (or fluidic media) in the different regions are necessarily identical in composition. Rather, the fluids in different fluidically connected regions of a microfluidic device can have different compositions (e.g., different concentrations of solutes, such as proteins, carbohydrates, ions, or other molecules) which are in flux as solutes move down their respective concentration gradients and/or fluids flow through the device.
A microfluidic (or nanofluidic) device can comprise “swept” regions and “unswept” regions. As used herein, a “swept” region is comprised of one or more fluidically interconnected circuit elements of a microfluidic circuit, each of which experiences a flow of medium when fluid is flowing through the microfluidic circuit. The circuit elements of a swept region can include, for example, regions, channels, and all or parts of chambers. As used herein, an “unswept” region is comprised of one or more fluidically interconnected circuit element of a microfluidic circuit, each of which experiences substantially no flux of fluid when fluid is flowing through the microfluidic circuit. An unswept region can be fluidically connected to a swept region, provided the fluidic connections are structured to enable diffusion but substantially no flow of media between the swept region and the unswept region. The microfluidic device can thus be structured to substantially isolate an unswept region from a flow of medium in a swept region, while enabling substantially only diffusive fluidic communication between the swept region and the unswept region. For example, a flow channel of a microfluidic device is an example of a swept region while an isolation region (described in further detail below) of a microfluidic device is an example of an unswept region.
As used herein, a “flow region” refers to one or more fluidically connected circuit elements (e.g. channel(s), region(s), chamber(s) and the like) that define, and are subject to, the trajectory of a flow of medium. A flow region is thus an example of a swept region of a microfluidic device. Other circuit elements (e.g., unswept regions) may be fluidically connected with the circuit elements that comprise the flow region without being subject to the flow of medium in the flow region.
As used herein, “alkyl” refers to a straight or branched hydrocarbon chain radical consisting solely of carbon and hydrogen atoms, containing no unsaturation, having from one to six carbon atoms (e.g., C1-C6 alkyl). Whenever it appears herein, a numerical range such as “1 to 6” refers to each integer in the given range; e.g., “1 to 6 carbon atoms” means that the alkyl group may consist of 1 carbon atom, 2 carbon atoms, 3 carbon atoms, etc., up to and including 6 carbon atoms, although the present definition also covers the occurrence of the term “alkyl” where no numerical range is designated. In some embodiments, it is a C1-C3 alkyl group. Typical alkyl groups include, but are in no way limited to, methyl, ethyl, propyl, isopropyl, n-butyl, iso-butyl, sec-butyl isobutyl, tertiary butyl, pentyl, isopentyl, neopentyl, hexyl, and the like. The alkyl is attached to the rest of the molecule by a single bond, for example, methyl (Me), ethyl (Et), n-propyl, 1-methylethyl (iso-propyl), n-butyl, n-pentyl, 1,1-dimethylethyl (t-butyl), hexyl, and the like.
Unless stated otherwise specifically in the specification, an alkyl group may be optionally substituted by one or more substituents which independently are: aryl, arylalkyl, heteroaryl, heteroarylalkyl, hydroxy, halo, cyano, trifluoromethyl, trifluoromethoxy, nitro, trimethylsilanyl, —OR′, SR′, —OC(O)—R′, —N(R′)2, —C(O)R′, C(O)OR′, —OC(O)N(R′)2, —C(O)N(R′)2, —N(R′)C(O)OR′, —N(R′)C(O)R′, —N(R′)C(O)N(R′)2, N(R′)C(NR′)N(R′)2, —N(R′)S(O)tR′(where t is 1 or 2), —S(O)tOR′(where t is 1 or 2), —S(O)tN(R′)2 (where t is 1 or 2), or PO3(R′)2 where each R′ is independently hydrogen, alkyl, fluoroalkyl, aryl, aralkyl, heterocycloalkyl, or heteroaryl.
As referred to herein, a fluorinated alkyl moiety is an alkyl moiety having one or more hydrogens of the alkyl moiety replaced by a fluoro substituent. A perfluorinated alkyl moiety has all hydrogens attached to the alkyl moiety replaced by fluoro substituents.
As referred to herein, a “halo” moiety is a bromo, chloro, or fluoro moiety.
As referred to herein, an “olefinic” compound is an organic molecule which contains an “alkene” moiety. An alkene moiety refers to a group consisting of at least two carbon atoms and at least one carbon-carbon double bond. The non-alkene portion of the molecule may be any class of organic molecule, and in some embodiments, may include alkyl or fluorinated (including but not limited to perfluorinated) alkyl moieties, any of which may be further substituted.
As used herein, a “densely packed hydrophobic monolayer” refers to a single layer of hydrophobic molecules that are packed sufficiently close together so as to resist intercalation and/or intrusion of polar molecules, such as water, ions, and other charged species.
As used herein, a “surfactant” refers to a molecule or population of molecules (e.g., a polymer or population of molecules with a polymeric component, wherein the length of the polymer or polymeric component may vary) comprising polar and non-polar moieties. The polar moiety can be nonionic, anionic, cationic, or zwitterionic and may be referred to as a head group. The presence of a surfactant in aqueous solution generally substantially lowers surface tension. Which parts of a surfactant form the head group and the hydrophobic moiety will generally be immediately apparent to one skilled in the art, in that the polar head group comprises hydrogen bond donors and/or acceptors or charged groups, whereas the hydrophobic moiety generally does not (e.g., as in a hydrocarbon chain). For example, in the surfactants sodium dodecyl sulfate and octylglucoside, the sodium sulfate and the glucoside are the polar head groups, while the dodecyl and octyl are the hydrophobic moieties.
As used herein: “μm” (or “um”) means micrometer; “μm3” means cubic micrometer; “pL” means picoliter, “nL” means nanoliter; and “μL” (or “uL”) means microliter.
The term “or” is used in an inclusive sense, i.e., equivalent to “and/or,” unless the context dictates otherwise.
Methods described herein can comprise synthesizing or amplifying nucleic acid and/or preparing nucleic acid libraries in microfluidic devices. Suitable microfluidic devices and related procedures are described below.
A. Methods of Loading into Microfluidic Devices.
Loading of micro-objects, such as biological micro-objects and/or beads, into different regions of a microfluidic device can involve the use of fluid flow, gravity, a dielectrophoresis (DEP) force, an electrowetting force, a magnetic force, or any combination thereof as described herein. The DEP force can be generated optically, such as by an optoelectronic tweezers (OET) configuration and/or electrically, such as by activation of electrodes/electrode regions in a temporal/spatial pattern. Similarly, the electrowetting force may be provided optically, such as by an opto-electro wetting (OEW) configuration and/or electrically, such as by activation of electrodes/electrode regions in a temporal spatial pattern.
B. Microfluidic Devices and Systems for Operating and Observing such Devices.
In some embodiments, the microfluidic device can include an enclosure having at least one microfluidic channel. In addition, the enclosure can include at least one microfluidic chamber (or sequestration pen) fluidically connected to the microfluidic channel. At least a portion of the substrate that defines the microchannel and/or the chamber can have an electrowetting configuration as described herein. The electrowetting configuration can be connected to a biasing potential and, while thus connected, change an effective wetting characteristic of any of a plurality of corresponding regions of the substrate surface (i.e., the droplet actuating surface). The wetting characteristic of the substrate surface can be changed sufficiently to move a liquid droplet across the substrate surface and between the microfluidic channel and the chamber. In the embodiment illustrated in
As generally illustrated in
The support structure 104 can be at the bottom and the cover 110 at the top of the microfluidic circuit 120, as illustrated in
The support structure 104 can comprise one or more electrodes (not shown) and a substrate or a plurality of interconnected substrates. The substrate can be any suitable substrate known in the art. For example, the support structure 104 can comprise one or more semiconductor substrates, each of which is electrically connected to at least one of the one or more electrodes (e.g., all or a subset of the semiconductor substrates can be electrically connected to a single electrode). Alternatively, the support structure 104 can comprise a printed circuit board assembly (“PCBA”) which comprises the one or more electrodes. In still other embodiments, the support structure 104 can comprise a substrate (e.g., a semiconductor substrate) which is mounted on a PCBA.
The microfluidic circuit structure 108 can define circuit elements of the microfluidic circuit 120. Such circuit elements can comprise spaces or regions that can be fluidly interconnected when microfluidic circuit 120 is filled with fluid, such as flow regions (which may include or be one or more flow channels), chambers, pens, traps, and the like. In the microfluidic circuit 120 illustrated in
The microfluidic circuit material 116 can be patterned with cavities or the like to define circuit elements and interconnections of the microfluidic circuit 120. The microfluidic circuit material 116 can comprise a flexible material, such as a flexible polymer (e.g. rubber, plastic, elastomer, silicone, polydimethylsiloxane (“PDMS”), or the like), which can be gas permeable. Other examples of materials that can compose microfluidic circuit material 116 include molded glass, an etchable material such as silicone (e.g. photo-patternable silicone or “PPS”), photo-resist (e.g., SU8), or the like. In some embodiments, such materials—and thus the microfluidic circuit material 116—can be rigid and/or substantially impermeable to gas. Regardless, the microfluidic circuit material 116 can be disposed on the support structure 104 and (optionally) inside the frame 114.
The cover 110 can be an integral part of the microfluidic circuit material 116 and/or the frame 114. Alternatively, the cover 110 can be a structurally distinct element, as illustrated in
In some embodiments, the cover 110 can comprise a rigid material. The rigid material may be glass or a material with similar properties. In some embodiments, the cover 110 can comprise a deformable material. The deformable material can be a polymer, such as PDMS. In some embodiments, the cover 110 can comprise both rigid and deformable materials. For example, one or more portions of cover 110 (e.g., one or more portions positioned over sequestration pens 124, 126, 128, 130) can comprise a deformable material that interfaces with rigid materials of the cover 110. In some embodiments, the cover 110 can further include one or more electrodes. The one or more electrodes can comprise a conductive oxide, such as indium-tin-oxide (ITO), which may be coated on glass or a similarly insulating material. Alternatively, the one or more electrodes can be flexible electrodes, such as single-walled nanotubes, multi-walled nanotubes, nanowires, clusters of electrically conductive nanoparticles, or combinations thereof, embedded in a deformable material, such as a polymer (e.g., PDMS). Flexible electrodes that can be used in microfluidic devices have been described, for example, in U.S. 2012/0325665 (Chiou et al.), the contents of which are incorporated herein by reference. In some embodiments, the cover 110 can be modified (e.g., by coating or conditioning all or part of a surface that faces inward toward the microfluidic circuit 120) to support droplet movement and/or cell adhesion, cell viability and/or cell growth. The modification may include a coating of a synthetic or natural polymer or a conditioned surface having covalently bound molecules (e.g., self-associating molecules). In some embodiments, the cover 110 and/or the support structure 104 can be transparent to light. The cover 110 may also include at least one material that is gas permeable (e.g., PDMS or PPS).
The electrical power source 192 can provide electric power to the microfluidic device 100 and/or tilting device 190, providing biasing voltages or currents as needed. The electrical power source 192 can, for example, comprise one or more alternating current (AC) and/or direct current (DC) voltage or current sources. The imaging device 194 can comprise a device, such as a digital camera, for capturing images inside microfluidic circuit 120. In some instances, the imaging device 194 further comprises a detector having a fast frame rate and/or high sensitivity (e.g. for low light applications). The imaging device 194 can also include a mechanism for directing stimulating radiation and/or light beams into the microfluidic circuit 120 and collecting radiation and/or light beams reflected or emitted from the microfluidic circuit 120 (or micro-objects contained therein). The emitted light beams may be in the visible spectrum and may, e.g., include fluorescent emissions. The reflected light beams may include reflected emissions originating from an LED or a wide spectrum lamp, such as a mercury lamp (e.g. a high pressure mercury lamp) or a Xenon arc lamp. As discussed with respect to
System 150 further comprises a tilting device 190 configured to rotate a microfluidic device 100 about one or more axes of rotation. In some embodiments, the tilting device 190 is configured to support and/or hold the enclosure 102 comprising the microfluidic circuit 120 about at least one axis such that the microfluidic device 100 (and thus the microfluidic circuit 120) can be held in a level orientation (i.e. at 0° relative to x- and y-axes), a vertical orientation (i.e. at 90° relative to the x-axis and/or the y-axis), or any orientation therebetween. The orientation of the microfluidic device 100 (and the microfluidic circuit 120) relative to an axis is referred to herein as the “tilt” of the microfluidic device 100 (and the microfluidic circuit 120). For example, the tilting device 190 can tilt the microfluidic device 100 at 0.1°, 0.2°, 0.3°, 0.4°, 0.5°, 0.6°, 0.7°, 0.8°, 0.9°, 1°, 2°, 3°, 4°, 5°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80°, 90°, or any degree therebetween relative to the x-axis or the y-axis. The level orientation (and thus the x- and y-axes) is defined as normal to a vertical axis defined by the force of gravity. The tilting device can also tilt the microfluidic device 100 (and the microfluidic circuit 120) to any degree greater than 90° relative to the x-axis and/or y-axis, or tilt the microfluidic device 100 (and the microfluidic circuit 120) 180° relative to the x-axis or the y-axis in order to fully invert the microfluidic device 100 (and the microfluidic circuit 120). Similarly, in some embodiments, the tilting device 190 tilts the microfluidic device 100 (and the microfluidic circuit 120) about an axis of rotation defined by flow region 106/channel 122 or some other portion of microfluidic circuit 120.
In some instances, the microfluidic device 100 is tilted into a vertical orientation such that the flow region 106/channel 122 is positioned above or below one or more sequestration pens. The term “above” as used herein denotes that the flow region 106/channel 122 is positioned higher than the one or more sequestration pens on a vertical axis defined by the force of gravity (i.e. an object in a sequestration pen above a flow region 106/channel 122 would have a higher gravitational potential energy than an object in the flow region/channel). The term “below” as used herein denotes that the flow region 106/channel 122 is positioned lower than the one or more sequestration pens on a vertical axis defined by the force of gravity (i.e. an object in a sequestration pen below a flow region 106/channel 122 would have a lower gravitational potential energy than an object in the flow region/channel).
In some instances, the tilting device 190 tilts the microfluidic device 100 about an axis that is parallel to the flow region 106/channel 122. Moreover, the microfluidic device 100 can be tilted to an angle of less than 90° such that the flow region 106/channel 122 is located above or below one or more sequestration pens without being located directly above or below the sequestration pens. In other instances, the tilting device 190 tilts the microfluidic device 100 about an axis perpendicular to the flow region 106/channel 122. In still other instances, the tilting device 190 tilts the microfluidic device 100 about an axis that is neither parallel nor perpendicular to the flow region 106/channel 122.
System 150 can further include a media source 178. The media source 178 (e.g., a container, reservoir, or the like) can comprise multiple sections or containers, each for holding a different fluidic medium 180. Thus, the media source 178 can be a device that is outside of and separate from the microfluidic device 100, as illustrated in
The master controller 154 can comprise a control module 156 and a digital memory 158. The control module 156 can comprise, for example, a digital processor configured to operate in accordance with machine executable instructions (e.g., software, firmware, source code, or the like) stored as non-transitory data or signals in the memory 158. Alternatively, or in addition, the control module 156 can comprise hardwired digital circuitry and/or analog circuitry. The media module 160, motive module 162, imaging module 164, tilting module 166, and/or other modules 168 can be similarly configured. Thus, functions, processes acts, actions, or steps of a process discussed herein as being performed with respect to the microfluidic device 100 or any other microfluidic apparatus can be performed by any one or more of the master controller 154, media module 160, motive module 162, imaging module 164, tilting module 166, and/or other modules 168 configured as discussed above. Similarly, the master controller 154, media module 160, motive module 162, imaging module 164, tilting module 166, and/or other modules 168 may be communicatively coupled to transmit and receive data used in any function, process, act, action or step discussed herein.
The media module 160 controls the media source 178. For example, the media module 160 can control the media source 178 to input a selected fluidic medium 180 into the enclosure 102 (e.g., through an inlet port 107). The media module 160 can also control removal of media from the enclosure 102 (e.g., through an outlet port (not shown)). One or more media can thus be selectively input into and removed from the microfluidic circuit 120. The media module 160 can also control the flow of fluidic medium 180 in the flow region 106/channel 122 inside the microfluidic circuit 120. For example, in some embodiments the media module 160 stops the flow of media 180 in the flow region 106/channel 122 and through the enclosure 102 prior to the loading of a micro-object or a bead into a sequestration pen (e.g., using gravity, electrowetting (EW) force, dielectrophoresis (DEP) force, or a combination thereof).
The motive module 162 can be configured to control selection, trapping, and movement of micro-objects and/or droplets of medium in the microfluidic circuit 120. As discussed in detail herein, the enclosure 102 can comprise an electrowetting (EW) configuration, such as an opto-electrowetting (OEW) configuration, an electrowetting on dielectric (EWOD) configuration, a single-sided electrowetting configuration, or the like. In certain embodiments, the enclosure 102 can further comprise a dielectrophoresis (DEP) configuration, such as an optoelectronic tweezer (OET) configuration, an electrically actuated DEP configuration, and the like. The motive module 162 can control the activation of electrodes and/or transistors (e.g., phototransistors) comprised by such EW and/or DEP configurations to select and move micro-objects and/or droplets of medium in the flow region 106/channel 122 and/or sequestration pens 124, 126, 128, 130.
The imaging module 164 can control the imaging device 194 (not shown). For example, the imaging module 164 can receive and process image data from the imaging device 194. Image data from the imaging device 194 can comprise any type of information captured by the imaging device 194 (e.g., the presence or absence of micro-objects, droplets of medium, accumulation of label, such as fluorescent label, etc.). Using the information captured by the imaging device 194, the imaging module 164 can further calculate the position of objects (e.g., micro-objects, droplets of medium, or the like) and/or the rate of motion of such objects within the microfluidic device 100.
The tilting module 166 can control the tilting motions of tilting device 190 (not shown). In addition, the tilting module 166 can control the tilting rate and timing, for example, to optimize transfer of micro-objects to the one or more sequestration pens via gravitational forces. The tilting module 166 is communicatively coupled with the imaging module 164 to receive data describing the motion of micro-objects and/or droplets of medium in the microfluidic circuit 120. Using this data, the tilting module 166 may adjust the tilt of the microfluidic circuit 120 in order to adjust the rate at which micro-objects and/or droplets of medium move in the microfluidic circuit 120. The tilting module 166 may also use this data to iteratively adjust the position of a micro-object and/or droplet of medium in the microfluidic circuit 120.
In the example shown in
The microfluidic circuit 120 may comprise any number of microfluidic sequestration pens. Although five sequestration pens are shown, microfluidic circuit 120 may have fewer or more sequestration pens. As shown, microfluidic sequestration pens 124, 126, 128, and 130 of microfluidic circuit 120 each comprise differing features and shapes which may provide one or more benefits useful for the manipulation of micro-objects and/or droplets of fluidic medium with the microfluidic device 100. Thus, in some embodiments, the microfluidic circuit 120 may comprise a plurality of microfluidic sequestration pens, wherein two or more of the sequestration pens comprise differing structures and/or features which provide differing benefits. In some embodiments, however, the microfluidic circuit 120 comprises a plurality of identical microfluidic sequestration pens. Microfluidic devices useful the manipulation of micro-objects and/or droplets of medium may include any of the sequestration pens 124, 126, 128, and 130, or variations thereof, including pens configured like those shown in
In the embodiment illustrated in
In some embodiments, microfluidic circuit 120 further comprises one or more micro-object traps 132. The traps 132 are generally formed in a wall forming the boundary of a flow region 106/channel 122, and may be positioned opposite an opening of one or more of the microfluidic sequestration pens 124, 126, 128, and 130. In some embodiments, the traps 132 are configured to receive or capture a single micro-object from the flow region 106/channel 122. In some embodiments, the traps 132 are configured to receive or capture a plurality of micro-objects from the flow region 106/channel 122. In some instances, the traps 132 comprise a volume approximately equal to the volume of a single target micro-object.
The traps 132 may further comprise an opening which is configured to assist the flow of targeted micro-objects into the traps 132. In some instances, the traps 132 comprise an opening having a height and width that is size according to the dimensions of a single target micro-object, whereby other micro-objects (or micro-objects that are greater in size) are prevented from entering into the micro-object trap. The traps 132 may further comprise other features configured to assist in retention of targeted micro-objects within the trap 132. In some instances, the trap 132 is aligned with and situated on the opposite side of a channel 122 relative to the opening of a microfluidic sequestration pen, such that upon tilting the microfluidic device 100 about an axis parallel to the channel 122, the trapped micro-object exits the trap 132 at a trajectory that causes the micro-object to fall into the opening of the sequestration pen. In some instances, the trap 132 comprises a side passage 134 that is smaller than the target micro-object in order to facilitate flow through the trap 132 and thereby increase the likelihood of capturing a micro-object in the trap 132.
As discussed in greater detail below, in some embodiments electrowetting (EW) forces are applied at one or more positions on the surface of the support structure 104 (and/or the cover 110) of the microfluidic device 100 (e.g., positions within the flow region and/or the sequestration pens) via one or more electrodes (not shown) to manipulate, transport, separate and sort droplets located in the microfluidic circuit 120. For example, in some embodiments, EW forces are applied at one or more positions on the surface of the support structure 104 (and/or the cover 110) to transfer a droplet from the flow region 106 into a desired microfluidic sequestration pen. In some embodiments, EW forces are used to prevent a droplet within a sequestration pen (e.g., sequestration pen 124, 126, 128, or 130) from being displaced therefrom. Further, in some embodiments, EW forces are used to selectively remove a droplet from a sequestration pen that was previously collected in accordance with the teachings of the instant disclosure. In some embodiments, the EW forces comprise opto-electrowetting (OEW) forces.
In some embodiments, dielectrophoretic (DEP) forces are applied across the fluidic medium 180 (e.g., in the flow region and/or in the sequestration pens) via one or more electrodes (not shown) to manipulate, transport, separate and sort micro-objects located therein. For example, in some embodiments, DEP forces are applied within one or more portions of microfluidic circuit 120 to transfer a single micro-object from the flow region 106 into a desired microfluidic sequestration pen. In some embodiments, DEP forces are used to prevent a micro-object within a sequestration pen (e.g., sequestration pen 124, 126, 128, or 130) from being displaced therefrom. Further, in some embodiments, DEP forces are used to selectively remove a micro-object from a sequestration pen that was previously collected in accordance with the teachings of the instant disclosure. In some embodiments, the DEP forces comprise optoelectronic tweezer (OET) forces.
In some embodiments, DEP and/or EW forces are combined with other forces, such as flow and/or gravitational force, so as to manipulate, transport, separate and sort micro-objects and/or droplets within the microfluidic circuit 120. For example, the enclosure 102 can be tilted (e.g., by tilting device 190) to position the flow region 106/channel 122 and micro-objects located therein above the microfluidic sequestration pens, and the force of gravity can transport the micro-objects and/or droplets into the pens. In some embodiments, the DEP and/or EW forces can be applied prior to the other forces. In other embodiments, the DEP and/or EW forces can be applied after the other forces. In still other instances, the DEP and/or EW forces can be applied at the same time as the other forces or in an alternating manner with the other forces.
C. Microfluidic Device Motive Configurations.
As described above, the control and monitoring equipment of the system can comprise a motive module for selecting and moving objects, such as micro-objects or droplets, in the microfluidic circuit of a microfluidic device. The microfluidic devices of the disclosure can have a variety of motive configurations, depending upon the type of object being moved and other considerations. In particular, the support structure 104 and/or cover 110 of the microfluidic device 100 can comprise an electrowetting (EW) configuration for selectively inducing EW forces on droplets in a fluidic medium 180 in the microfluidic circuit 120 and thereby select, capture, and/or move individual droplets or groups of droplets. In certain embodiments, the microfluidic devices of the disclosure can comprise a first section having an EW configuration and a second section having a dielectrophoresis (DEP) configuration. Thus, at least a section of the support structure 104 and/or cover 110 of the microfluidic device 100 can comprise a DEP configuration for selectively inducing DEP forces on micro-objects in a fluidic medium 180 in the microfluidic circuit 120 and thereby select, capture, and/or move individual micro-objects or groups of micro-objects
D. Electrowetting Configurations.
In certain embodiments, a microfluidic device of the disclosure can comprise an electrowetting configuration which includes a substrate having a dielectric layer and a droplet actuation surface, the droplet actuation surface comprising (or consisting of, or consisting essentially of) a hydrophobic layer (i.e., an outer hydrophobic layer) covalently bonded to the surface of an underlying dielectric layer (i.e., an inner dielectric layer). When the microfluidic device is operatively connected to a voltage source, an aqueous droplet resting upon or otherwise contacting the hydrophobic layer can be reliably and robustly wetted, and thereby moved, by an electrowetting force. The dielectric layer can be located beneath the hydrophobic layer such that a droplet resting on the substrate directly contacts the hydrophobic layer.
The microfluidic device can comprise a base that includes the substrate, and the substrate can further have at least one electrode (e.g., a first electrode) configured to be connected to the voltage source (e.g., an AC voltage source), the at least one electrode being electrically coupled to the inner dielectric layer. In some embodiments, the microfluidic device further comprises a cover and at least one spacing element. The substrate and the cover can be substantially parallel to one another and joined together by the spacing element to define an enclosure configured to hold a liquid medium. In such embodiments, the cover can include at least one electrode configured to be connected to the voltage source (e.g., the AC voltage source). In some embodiments, the microfluidic device can comprise a single-sided electrowetting configuration. In such embodiments, the microfluidic device need not include a cover. For example, the base can include the substrate and a first electrode configured to be connected to a voltage source (e.g., an AC voltage source), and the substrate can include a second electrode (e.g., a mesh electrode) configured to be connected to the voltage source.
As shown, apparatus 400 can include a base 104 which comprises the substrate and at least one electrode (e.g., a first electrode) 418. The substrate can comprise various layers, including an outer hydrophobic layer 412, an inner dielectric layer 414, a semi-conductive layer 416, an electrode 418, and optionally a support 420. The hydrophobic layer 412 and the inner dielectric layer 414 can provide an inward-facing surface of the substrate 102 that defines, in part, the enclosure.
Apparatus 400 also includes a cover 110, which includes an outer hydrophobic layer 422, an inner layer 428, which may comprise the at least one electrode, and optionally a support 430. Cover 110 and base 104 are substantially parallel to one another and joined together by a spacing element 108 (e.g., microfluidic circuit material) so as to define an enclosure 435 configured to hold a liquid medium. The liquid medium can be, for example, a hydrophobic liquid, such as an organic liquid. In addition, the enclosure 435 can hold a droplet of liquid 440, such as an aqueous medium. Typically, the liquid medium and the liquid of the droplet are selected to be immiscible liquids.
The spacing element 108 can comprise a polymer. The polymer can be, for example, a silicon-based organic polymer, such as polydimethylsiloxane (PDMS) or photo-patternable silicone (PPS), both available from Dow Corning. Alternatively, the spacing element 108 can comprise an epoxy-based adhesive. The epoxy-based adhesive can be, for example, SU-8 or equivalent types of materials. The spacing element 108 can have a thickness (i.e., the gap between the inner surface of the substrate 104 and the cover 110, which could also be described as “height”) of at least 30, 40, 50, 60, 70, 80, 90, 100, or more microns. Thus, for example, the thickness of spacing element 108 can be 30-60 microns, 40-80 microns, 50-100 microns, 60-120 microns, 70-140 microns, 75-150 microns, 80-160 microns, 90-180 microns, or 100-200 microns.
The spacing element 108 can define one or more microfluidic channels within the enclosure. In addition, the spacing element 108 can further define a plurality of chambers (or sequestration pens) within the enclosure, wherein each chamber is fluidically connected to and opens off of at least one microfluidic channel. Thus, for example, the spacing element 108 can define a single microfluidic channel and a plurality of chambers fluidically connected thereto, or a plurality of microfluidic channels with each channel fluidically connected to a plurality of chambers. Furthermore, each chamber can be fluidically connected to more than one microfluidic channel, as illustrated in
When the at least one electrode 418 of the substrate 104 and the at least one electrode 428 of the cover 110 are connected to opposing terminals of an AC voltage source (not shown), the substrate 104 is capable of applying an electrowetting force to aqueous droplets in contact with the outer hydrophobic surface 412 (i.e., the droplet actuation surface) of the substrate 104. In certain embodiments, the AC voltage used to achieve electrowetting-based movement of a droplet in the microfluidic device is at least 20 Volts peak-to-peak (ppV) (e.g., about 20 to 80 ppV, about 20 to 60 ppV, about 25 to 50 ppV, about 25 to 40 ppV, or about 25 to 35 ppV). In certain embodiments, the frequency of the AC voltage used to achieve electrowetting-based movement of a droplet in the microfluidic device is about 1 to 100 kHz (e.g., about 5 to 90 kHz, about 10 to 80 kHz, about 15 to 70 kHz, about 20 to 60 kHz, about 25 to 50 kHz, or about 30 to 40 kHz).
The outer hydrophobic layer 412 of the substrate 104 and the outer hydrophobic layer 422 of the cover 110 can each comprise a densely packed monolayer of self-associating molecules covalently bound to the inner dielectric layer 414 of the substrate 104 or the inner layer 428 of the cover 110, respectively. The self-associating molecules of the monolayer comprise sufficient two-dimensional packing density so as to create a hydrophobic barrier between a surface to which the monolayer is bound and a hydrophilic liquid (i.e., to prevent intercalation and/or penetration of polar molecules or other chemical species into the monolayer). The packing density of a densely packed monolayer will depend on the self-associating molecules used. A densely packed monolayer comprising alkyl-terminated siloxane will typically comprise at least 1×1014 molecules/cm2 (e.g., at least 1.5×1014, 2.0×1014, 2.5×1014, or more molecules/cm2).
As described in greater detail below, the self-associating molecules can each comprise a linking group, such as a siloxane group or a phosphonic acid group. The siloxane groups can be covalently bonded to the molecules of the inner dielectric layer 414 or inner layer 428. Similarly, the phosphonic acid groups can be covalently bonded to the molecules of the inner dielectric layer 414 or inner layer 428. The self-associating molecules can comprise long-chain hydrocarbons, which can be unbranched. Thus, the self-associating molecules can comprise alkyl-terminated siloxane or alkyl-terminated phosphonic acid. The long-chain hydrocarbons can comprise a chain of at least 10 carbons (e.g., at least 16, 18, 20, 22, or more carbons). The self-associating molecules can comprise fluorinated carbon chains. Thus, for example, the self-associating molecules can comprise fluoroalkyl-terminated siloxane or fluoroalkyl-terminated phosphonic acid. The fluorinated carbon chains can have the chemical formula CF3—(CF2)m—(CH2)n-, wherein m is at least 2, n is 0,1,2, or greater, and m+n is at least 9.
The monolayer of self-associating molecules can have a thickness of less than about 5 nanometers (e.g., about 1.0 to about 4.0 nanometers, about 1.5 to about 3.0 nanometers, or about 2.0 to about 2.5 nanometers).
The outer hydrophobic layer 412 of the substrate 104 can be patterned such that select regions are relatively hydrophilic compared to the remainder of the outer hydrophobic layer. This can be achieved, for example, by increasing the voltage drop across the underlying inner dielectric layer 122 to 50 ppV or greater (e.g., 60, 65, 70, 75, 80, or more ppV) for a period of time. Without intending to be bound by theory, it is believed that the relatively hydrophilic regions comprise water molecules that have intercalated into the monolayer.
1. Dielectric Layer(s) and Stacks
In some embodiments, the inner dielectric layer of the substrate can comprise one or more oxide layers. In some embodiments, the inner dielectric layer of the substrate can comprise a first layer of dielectric material. For example, the inner dielectric layer can consist of a single layer of dielectric material (e.g., aluminum oxide, hafnium oxide, or the like). For example, the inner dielectric layer can comprise or consist of a single oxide layer, such as a metal oxide layer. In certain embodiments, the first oxide layer is formed by atomic layer deposition (ALD).
Alternatively, the inner dielectric layer can be a dielectric stack that comprises two or more layers of dielectric material. Thus, in certain embodiments, the inner dielectric layer can comprise a first layer of dielectric material and a second layer of dielectric material. The first layer of dielectric material can comprise an oxide, such as a metal oxide (e.g., aluminum oxide, hafnium oxide, or the like); and the second layer of dielectric material can comprise an oxide, such as silicon oxide, or a nitride, such as silicon nitride. In such embodiments, the first layer of dielectric material can have a first surface that contacts the second layer of dielectric material and an opposing surface to which the hydrophobic layer is covalently bound. In certain embodiments, the second layer of dielectric material can have a thickness of about 30 nm to about 100 nm, depending upon the type of dielectric material used. For example, the second layer of dielectric material can comprise silicon oxide and can have a thickness of about 30 nm to about 50 nm, or about 30 nm to about 40 nm. Alternatively, the second layer of dielectric material can comprise silicon nitride and can have a thickness of about 50nm to about 100 nm, or about 80 nm to about 100 nm. In certain embodiments, the second layer of dielectric material is formed by ALD. In other embodiments, the second layer of dielectric material is formed by a Plasma Enhanced Chemical Vapor Deposition (PECVD) technique. In certain embodiments, the first layer of dielectric material can have a thickness of about 1 nm to about 50 nm (e.g., about 1 nm to about 10 nm, about 2 nm to about 5 nm, about 5 nm to about 10 nm, about 5 nm to about 15 nm, about 10 nm to about 20 nm, about 15 nm to about 25 nm, about 20 nm to about 30 nm, about 25 nm to about 35 nm, about 30 nm to about 40 nm, about 35 nm to about 45 nm, about 40 nm to about 50 nm, or any range defined by two of the foregoing endpoints) and can be formed by ALD. In some embodiments, the first layer of dielectric material is formed by PECVD (e.g., comprising silicon oxide or silicon nitride), optionally wherein the second layer is formed by ALD (e.g., comprising a metal oxide, such as aluminum oxide or hafnium oxide). Thus, for example, the metal oxide layer can be deposited by an Atomic Layer Deposition (ALD) technique and the layer comprising silicon dioxide or silicon nitride can be deposited by a Plasma Enhanced Chemical Vapor Deposition (PECVD) technique. In certain embodiments, the thickness of the metal oxide layer can range from about 1 nm to about 15 nm, about 5 nm to about 20 nm, about 15 nm to about 45 nm, or about 30 nm to about 40 nm, or about 33 nm to about 36 nm.
In yet other embodiments, the inner dielectric stack can comprise a third layer of dielectric material, with the third layer of dielectric material have a first surface that contact the first layer of dielectric material and an opposing surface that is covalently bonded to the hydrophobic layer. In such embodiments, the first layer of dielectric material can comprise an oxide, as described above (or elsewhere herein), and the second layer of dielectric material can comprise an oxide or a nitride, as described above (or elsewhere herein). In some embodiments, the first layer comprises silicon oxide or silicon nitride and is formed by PECVD. In some embodiments, the second layer comprises a metal oxide and is formed by ALD, optionally wherein the first layer comprises silicon oxide or silicon nitride and is formed by PECVD. In certain embodiments, the third layer of dielectric material can comprise an oxide, such as silicon dioxide or other dielectric materials that bond well to linkers such as siloxane groups or phosphonic acid groups. In certain embodiments, the third layer of dielectric material is deposited by ALD, optionally wherein the third layer comprises silicon oxide, further optionally wherein the second layer comprises a metal oxide and is formed by ALD and the first layer comprises silicon oxide or silicon nitride and is formed by PECVD. In some embodiments, a first layer can comprise a metal oxide, such as aluminum oxide, hafnium oxide, or the like, which can be sandwiched between a silicon dioxide layer and a silicon nitride layer. In certain embodiments, the thickness of the metal oxide layer can range from about 5 nm to about 20 nm, and the layer can be deposited by an Atomic Layer Deposition (ALD) technique. The silicon oxide layer can also be deposited by ALD, and can have a thickness of about 1 nm to about 10 nm. The silicon nitride layer can be deposited by a Plasma Enhanced Chemical Vapor Deposition (PECVD) technique has and can have a thickness of about 80 nm to about 100 nm, or about 90 nm thickness. In certain embodiments, a third layer of dielectric material has a thickness of about 1 nm to about 10 nm, or about 4 nm to about 6 nm.
Regardless of the number of layers that make up the inner dielectric stack, the inner dielectric layer can have a total thickness of at least about 40 nm (e.g., about 40 nm to about 120 nm, about 40 nm to about 60 nm, about 50 nm to about 70 nm, about 60 nm to about 80 nm, about 70 nm to about 90 nm, about 80 nm to about 100 nm, about 90 nm to about 110 nm, about 100 nm to about 120 nm, or a range defined by any two of the foregoing endpoints). Likewise, the dielectric stack can have an impedance of about 50 kOhms to about 150 kOhms (e.g., about 50 kOhms to about 75 kOhms, about 75 kOhms to about 100 kOhms, about 100 kOhms to about 125 kOhms, about 125 kOhms to about 150 kOhms, or a range defined by any two of the foregoing endpoints). In some embodiments, the inner dielectric layer can have a thickness of about 50 to 105 nanometers and/or an impedance of about 50 to 150 kOhms, e.g., about 100 kOhms.
A summary of exemplary embodiments of the dielectric layer is provided as follows.
In certain embodiments, the dielectric layer is a single layer of metal oxide, deposited by ALD. Examples of the metal oxide for the first layer include, e.g., aluminum oxide and hafnium oxide. The thickness of the single layer can be adjusted to achieve an electrical impedance of about 50 kOhms to about 150 kOhms (e.g., about 100 kOhms). In some embodiments, the impedance is as described above.
In some embodiments, a first layer is provided comprising a metal oxide, e.g., aluminum oxide and hafnium oxide, which is deposited by ALD. A second layer is deposited on the first layer by ALD. The second layer is formed of silicon oxide or other material that bonds well to siloxane linkers in the molecules that make up the surface coating. The thickness of the first layer can be from about 1 nm to about 10 nm (e.g., about 2nm to about 5 nm). The thickness of the second layer can be from about 1 nm to about 10 nm (e.g., about 2nm to about 5 nm).
In other embodiments, a first layer of silicon oxide (or silicon nitride, or the like) is formed by plasma enhanced chemical vapor deposition (PECVD). A second layer is deposited on the first layer and formed of a metal oxide (e.g., aluminum oxide or hafnium oxide) deposited by ALD.
The total thickness of the two-layer dielectric stack can be adjusted to ensure an electrical impedance of about 50 kOhms to about 150 kOhms (e.g., about 100 kOhms). In some embodiments, the impedance is as described above.
In some embodiments, a first layer of silicon oxide (or silicon nitride, or the like) is formed by plasma enhanced chemical vapor deposition (PECVD). A second layer is provided on top of the first layer and formed of a metal oxide (e.g., aluminum oxide or hafnium oxide) deposited by ALD. The second layer has a thickness of about 1 nm to 10 nm (e.g., about 2 nm to about 5 nm).
A third layer is further provided on top of the second layer, with the third layer formed of silicon oxide (or another dielectric material that can bond well to siloxane linkers in the molecules that make up the surface coating). The third layer should also be formed by ALD, with a thickness of about 1 nm to about 10 nm (e.g., about 2-5 nm).
The total thickness of the three-sublayer dielectric stack can be adjusted to achieve an electrical impedance of about 50 kOhms to about 150 kOhms (e.g., about 100 kOhms). In some embodiments, the impedance is as described above.
2. Photoresponsive Layer
The substrate 104 can comprise a semi-conductive layer 416 having a first side that contacts the inner dielectric layer 414, and a second side that contacts the at least one electrode 418, thereby electrically coupling the inner dielectric layer 414 with the electrode 418. The semi-conductive layer 416 can be photoresponsive. For example, the photoresponsive layer 416 can comprise hydrogenated amorphous silicon (a-Si:H). The a-Si:H can comprise about 8% to 40% hydrogen (i.e., calculated as 100 * the number of hydrogen atoms/total number of hydrogen and silicon atoms). The a-Si:H layer can have a thickness of at least about 500 nanometers (e.g., at least about 600 to 1400, about 700 to 1300, about 800 to 1200, about 900 to 1100, or about 1000 nanometers). However, the thickness of the a-Si:H layer can be varied in accordance with the thickness of the inner dielectric layer 414 so as to achieve a suitable difference between the impedance of the inner dielectric layer 414 and the impedance of the a-Si:H layer when the substrate 104 is in the on state (i.e., illuminated and conducting) and the off state (i.e., dark and non-conducting). For example, the impedance of the inner dielectric layer 414 can be tuned to about 50 kOhms to about 150 kOhms, and the impedance of the a-Si:H layer can be tuned to at least about 0.5 MOhms in the off state and less than or equal to about 1 kOhms in the on state. These are only examples, but they illustrate how the impedances can be tuned to achieve a photoresponsive (in this case, photoconductive) layer 416 displaying robust on/off performance.
In embodiments where the semi-conductive layer 416 has a photoresponsive layer formed from a-Si:H layer, the substrate 104 can optionally include additional components. For example, the semi-conductive layer 416 can include an array of phototransistors, such as described in U.S. Pat. No. 7,956,339 (Chiou et al.) or U.S. Pat. No. 9,908,115 (Hobbs et al.), the contents of which are incorporated herein by reference. The a-Si:H layer can be deposited on top of the array of phototransistors, as described in PCT Publication No. WO 2017/075295 (Lowe et al.), the contents of which are incorporated herein by reference. Alternatively, or in addition, the semi-conductive layer 416 can include floating electrode pads located between the a-Si:H layer and the inner dielectric layer 414. Such floating electrode pads have been described, for example, in U.S. Pat. No. 6,958,132, the contents of which are incorporated herein by reference.
The semi-conductive layer 416 can, alternatively, comprise a plurality of conductors, each conductor controllably connectable to the at least one electrode of the substrate 102 via a transistor switch. The transistor switch can be a phototransistor switch. Conductors controlled by transistor switches are well-known in the art and have been described, e.g., in U.S. Pat. No. 9,403,172 (Short et al.), U.S. Pat. No. 6,942,776 (Medoro), and U.S. Pat. No. 6,294,063 (Becker et al.), the contents of each of which are incorporated herein by reference.
The substrate 104 can comprise a single electrode 418 configured to be connected to an AC voltage source. The single electrode 418 can comprising a layer of indium-tin-oxide (ITO), which can, for example, be formed upon by a glass support 420. Alternatively, the single electrode 418 can comprise a layer of electrically conductive silicon. In other embodiments, the substrate 104 can comprise a plurality of electrodes that are individually addressable, as in the manner of EWOD devices, which are well-known in the art. The individually addressable electrodes can be connectable to one or more AC voltage sources via corresponding transistor switches.
3. Cover; Additional Layers Associated with Cover
For embodiments in which the microfluidic device comprises a cover, a surface of the cover that faces inward toward the enclosure can include an inner layer and a hydrophobic layer (i.e., an outer hydrophobic layer) covalently bonded to the inner layer. Similar to the outer hydrophobic layer of the substrate, the outer hydrophobic layer of the cover can comprise self-associating molecules covalently bonded to the inner layer so as to form a densely-packed hydrophobic monolayer. Thus, the outer hydrophobic layer can comprise any of the self-associating molecules described above (or elsewhere herein) for the outer hydrophobic layer of the substrate. In some embodiments, the outer hydrophobic layer of the cover comprises the same self-associating molecules as the outer hydrophobic layer of the substrate. In other embodiments, the outer hydrophobic layer of the substrate has a different type (or types) of self-associating molecules as the outer hydrophobic layer of the substrate. Thus, the cover 110 can, in the manner of the substrate, further comprise a dielectric layer (not shown) juxtaposed to the hydrophobic layer 422, and a conductive layer (not shown) juxtaposed between the dielectric layer and the electrode 428. Thus, the microfluidic apparatus 400 can have both the substrate 104 and the cover 110 configured to provide an electrowetting force to an aqueous droplet 440 located within the enclosure 435. In such embodiments, the dielectric layer of the cover 110 can be configured in any of the ways disclosed herein for the inner dielectric layer 414 of the substrate 104, and the conductive layer of the cover 104 can be configured in any of the ways disclosed herein for the conductive layer 126 of the substrate 102
In some embodiments, the outer hydrophobic layer of the inward-facing surface of the cover has a thickness of less than 5 nanometers (e.g., about 1.5 to 3.0 nanometers). In some embodiments, the outer hydrophobic layer of the inward-facing surface of the cover can be patterned such that select regions are relatively hydrophilic compared to the remainder of the outer hydrophobic layer.
4. Integration with Electro Positioning Apparatus
In some embodiments, an electrowetting apparatus is integrated with an electro positioning apparatus. For example, in some embodiments, a microfluidic device can include a substrate having an electrowetting configuration and a portion of a substrate can further comprise a dielectrophoresis (DEP) configuration. Exemplary DEP configurations are discussed in detail below. Thus, the substrate can be monolithic. Alternatively, the microfluidic device or apparatus can include a first module or section having a first substrate that has a dielectrophoresis (DEP) configuration, and a second module or section having a second substrate that includes an electrowetting configuration. Such devices can be considered as having a duolithic substrate, and there can be a bridge between the first module or section and the second module or section that provides integration of the functionalities associated with each substrate and its particular configuration. The bridge can include tubing or the like that connects two otherwise discrete devices. Alternatively, the bridge can comprise a bonding agent that brings the substrates into close juxtaposition (e.g., within 2 mm, 1.5 mm, 1.0 mm, 0.5 mm, or less). In yet other alternatives, the bridge can be a non-functional region on a monolithic substrate, wherein the zone of non-functionality is where the substrate configuration switches from one configuration (e.g., an electrowetting configuration) to another configuration (e.g., a DEP configuration). Regardless of whether the microfluidic device has a monolithic or duolithic substrate (or even a multi-lithic substrate), each of the electrowetting configuration and the DEP configuration can be any such configuration known in the art or disclosed herein. For example, the electrowetting configuration can be an opto-electrowetting (OEW) configuration, an electrowetting on dielectric (EWOD) configuration, a single-sided electrowetting configuration, or the like. Similarly, the DEP configuration can be an optoelectronic tweezer (OET) configuration, such as provided by photoconductive substrate comprising a layer of amorphous silicon and/or an array of phototransistors, an array of electrodes controlled by phototransistors, an array of electrodes electrically actuated, or the like. In certain alternative embodiments, the substrate can comprise an electrowetting configuration but lack any additional configuration (e.g., lack a dielectrophoresis (DEP) configuration).
E. Dielectrophoresis (DEP) Configurations.
As discussed herein, the microfluidic devices of the disclosure can include a section having a DEP configuration. One example of such as section is microfluidic device 200 illustrated in
As seen in
In certain embodiments, the microfluidic device 200 illustrated in
With the power source 212 activated, the foregoing DEP configuration creates an electric field gradient in the fluidic medium 180 between illuminated DEP electrode regions 214a and adjacent dark DEP electrode regions 214, which in turn creates local DEP forces that attract or repel nearby micro-objects (not shown) in the fluidic medium 180. DEP electrodes that attract or repel micro-objects in the fluidic medium 180 can thus be selectively activated and deactivated at many different such DEP electrode regions 214 at the inner surface 208 of the region/chamber 202 by changing light patterns 218 projected from a light source 216 into the microfluidic device 200. Whether the DEP forces attract or repel nearby micro-objects can depend on such parameters as the frequency of the power source 212 and the dielectric properties of the medium 180 and/or micro-objects (not shown).
The square pattern 220 of illuminated DEP electrode regions 214a illustrated in
In some embodiments, the electrode activation substrate 206 can comprise or consist of a photoconductive material. In such embodiments, the inner surface 208 of the electrode activation substrate 206 can be featureless. For example, the electrode activation substrate 206 can comprise or consist of a layer of hydrogenated amorphous silicon (a-Si:H). The a-Si:H can comprise, for example, about 8% to 40% hydrogen (calculated as 100 * the number of hydrogen atoms/the total number of hydrogen and silicon atoms). The layer of a-Si:H can have a thickness of about 500 nm to about 2.0 □ m. In such embodiments, the DEP electrode regions 214 can be created anywhere and in any pattern on the inner surface 208 of the electrode activation substrate 206, in accordance with the light pattern 218. The number and pattern of the DEP electrode regions 214 thus need not be fixed, but can correspond to the light pattern 218. Examples of microfluidic devices having a DEP configuration comprising a photoconductive layer such as discussed above have been described, for example, in U.S. Patent No. RE 44,711 (Wu et al.) (originally issued as U.S. Pat. No. 7,612,355), the entire contents of which are incorporated herein by reference.
In other embodiments, the electrode activation substrate 206 can comprise a substrate comprising a plurality of doped layers, electrically insulating layers (or regions), and electrically conductive layers that form semiconductor integrated circuits, such as is known in semiconductor fields. For example, the electrode activation substrate 206 can comprise a plurality of phototransistors, including, for example, lateral bipolar phototransistors, each phototransistor corresponding to a DEP electrode region 214. Alternatively, the electrode activation substrate 206 can comprise electrodes (e.g., conductive metal electrodes) controlled by phototransistor switches, with each such electrode corresponding to a DEP electrode region 214. The electrode activation substrate 206 can include a pattern of such phototransistors or phototransistor-controlled electrodes. The pattern, for example, can be an array of substantially square phototransistors or phototransistor-controlled electrodes arranged in rows and columns, such as shown in
Examples of microfluidic devices having electrode activation substrates that comprise phototransistors have been described, for example, in U.S. Pat. No. 7,956,339 (Ohta et al.) (see, e.g., device 300 illustrated in
In some embodiments of a DEP configured microfluidic device, the top electrode 210 is part of a first wall (or cover 110) of the enclosure 102, and the electrode activation substrate 206 and bottom electrode 204 are part of a second wall (or support structure 104) of the enclosure 102. The region/chamber 202 can be between the first wall and the second wall. In other embodiments, the electrode 210 is part of the second wall (or support structure 104) and one or both of the electrode activation substrate 206 and/or the electrode 210 are part of the first wall (or cover 110). Moreover, the light source 216 can alternatively be used to illuminate the enclosure 102 from below.
With the microfluidic device 200 of
In other embodiments, the microfluidic device 200 can have a DEP configuration that does not rely upon light activation of DEP electrodes at the inner surface 208 of the electrode activation substrate 206. For example, the electrode activation substrate 206 can comprise selectively addressable and energizable electrodes positioned opposite to a surface including at least one electrode (e.g., cover 110). Switches (e.g., transistor switches in a semiconductor substrate) may be selectively opened and closed to activate or inactivate DEP electrodes at DEP electrode regions 214, thereby creating a net DEP force on a micro-object (not shown) in region/chamber 202 in the vicinity of the activated DEP electrodes. Depending on such characteristics as the frequency of the power source 212 and the dielectric properties of the medium (not shown) and/or micro-objects in the region/chamber 202, the DEP force can attract or repel a nearby micro-object. By selectively activating and deactivating a set of DEP electrodes (e.g., at a set of DEP electrodes regions 214 that forms a square pattern 220), one or more micro-objects in region/chamber 202 can be trapped and moved within the region/chamber 202. The motive module 162 in
F. Microfluidic Devices with Electrowetting (EW) and Dielectrophoresis (DEP) Configurations.
Section 470 of microfluidic device 450 comprises a dielectrophoresis DEP configuration, which includes a base 104, a first electrode 479, an electrode activation substrate 474, and an inward-facing surface that defines, in part, the enclosure 475. Section 470 further includes a cover 110 comprising an electrode 468, and microfluidic circuit material 108 that connects the base 104 with the cover 110 and further helps to define the microfluidic circuit of the DEP section.
As shown in
In one embodiment as depicted in
G. Sequestration Pens.
Non-limiting examples of generic sequestration pens 224, 226, and 228 are shown within the microfluidic device 230 depicted in
The sequestration pens 224, 226, and 228 of
The channel 122 can thus be an example of a swept region, and the isolation regions 240 of the sequestration pens 224, 226, 228 can be examples of unswept regions. As noted, the channel 122 and sequestration pens 224, 226, 228 can be configured to contain one or more fluidic media 180. In the example shown in
As is known, a flow 242 of fluidic medium 180 in a microfluidic channel 122 past a proximal opening 234 of sequestration pen 224 can cause a secondary flow 244 of the medium 180 into and/or out of the sequestration pen 224. To isolate micro-objects 246 in the isolation region 240 of a sequestration pen 224 from the secondary flow 244, the length Lcon of the connection region 236 of the sequestration pen 224 (i.e., from the proximal opening 234 to the distal opening 238) should be greater than the penetration depth Dp of the secondary flow 244 into the connection region 236. The penetration depth Dp of the secondary flow 244 depends upon the velocity of the fluidic medium 180 flowing in the channel 122 and various parameters relating to the configuration of the channel 122 and the proximal opening 234 of the connection region 236 to the channel 122. For a given microfluidic device, the configurations of the channel 122 and the opening 234 will be fixed, whereas the rate of flow 242 of fluidic medium 180 in the channel 122 will be variable. Accordingly, for each sequestration pen 224, a maximal velocity Vmax for the flow 242 of fluidic medium 180 in channel 122 can be identified that ensures that the penetration depth Dp of the secondary flow 244 does not exceed the length Lcon of the connection region 236. As long as the rate of the flow 242 of fluidic medium 180 in the channel 122 does not exceed the maximum velocity Vmax, the resulting secondary flow 244 can be limited to the channel 122 and the connection region 236 and kept out of the isolation region 240. The flow 242 of medium 180 in the channel 122 will thus not draw micro-objects 246 out of the isolation region 240. Rather, micro-objects 246 located in the isolation region 240 will stay in the isolation region 240 regardless of the flow 242 of fluidic medium 180 in the channel 122.
Moreover, as long as the rate of flow 242 of medium 180 in the channel 122 does not exceed Vmax, the flow 242 of fluidic medium 180 in the channel 122 will not move miscellaneous particles (e.g., microparticles and/or nanoparticles) from the channel 122 into the isolation region 240 of a sequestration pen 224. Having the length Lcon of the connection region 236 be greater than the maximum penetration depth Dp of the secondary flow 244 can thus prevent contamination of one sequestration pen 224 with miscellaneous particles from the channel 122 or another sequestration pen (e.g., sequestration pens 226, 228 in
Because the channel 122 and the connection regions 236 of the sequestration pens 224, 226, 228 can be affected by the flow 242 of medium 180 in the channel 122, the channel 122 and connection regions 236 can be deemed swept (or flow) regions of the microfluidic device 230. The isolation regions 240 of the sequestration pens 224, 226, 228, on the other hand, can be deemed unswept (or non-flow) regions. For example, components (not shown) in a first fluidic medium 180 in the channel 122 can mix with a second fluidic medium 248 in the isolation region 240 substantially only by diffusion of components of the first medium 180 from the channel 122 through the connection region 236 and into the second fluidic medium 248 in the isolation region 240. Similarly, components (not shown) of the second medium 248 in the isolation region 240 can mix with the first medium 180 in the channel 122 substantially only by diffusion of components of the second medium 248 from the isolation region 240 through the connection region 236 and into the first medium 180 in the channel 122. In some embodiments, the extent of fluidic medium exchange between the isolation region of a sequestration pen and the flow region by diffusion is greater than about 90%, 91%, 92%, 93%, 94% 95%, 96%, 97%, 98%, or greater than about 99% of fluidic exchange. The first medium 180 can be the same medium or a different medium than the second medium 248. Moreover, the first medium 180 and the second medium 248 can start out being the same, then become different (e.g., through conditioning of the second medium 248 by one or more cells in the isolation region 240, or by changing the medium 180 flowing through the channel 122).
The maximum penetration depth Dp of the secondary flow 244 caused by the flow 242 of fluidic medium 180 in the channel 122 can depend on a number of parameters, as mentioned above. Examples of such parameters include: the shape of the channel 122 (e.g., the channel can direct medium into the connection region 236, divert medium away from the connection region 236, or direct medium in a direction substantially perpendicular to the proximal opening 234 of the connection region 236 to the channel 122); a width Wch (or cross-sectional area) of the channel 122 at the proximal opening 234; and a width Wcon (or cross-sectional area) of the connection region 236 at the proximal opening 234; the velocity V of the flow 242 of fluidic medium 180 in the channel 122; the viscosity of the first medium 180 and/or the second medium 248, or the like.
In some embodiments, the dimensions of the channel 122 and sequestration pens 224, 226, 228 can be oriented as follows with respect to the vector of the flow 242 of fluidic medium 180 in the channel 122: the channel width Wch (or cross-sectional area of the channel 122) can be substantially perpendicular to the flow 242 of medium 180; the width Wcon (or cross-sectional area) of the connection region 236 at opening 234 can be substantially parallel to the flow 242 of medium 180 in the channel 122; and/or the length Lcon of the connection region can be substantially perpendicular to the flow 242 of medium 180 in the channel 122. The foregoing are examples only, and the relative position of the channel 122 and sequestration pens 224, 226, 228 can be in other orientations with respect to each other.
As illustrated in
As illustrated in
The microfluidic device 250 of
Each sequestration pen 266 can comprise an isolation structure 272, an isolation region 270 within the isolation structure 272, and a connection region 268. From a proximal opening 274 at the channel 264 to a distal opening 276 at the isolation structure 272, the connection region 268 fluidically connects the channel 264 to the isolation region 270. Generally, in accordance with the above discussion of
In various embodiments of sequestration pens (e.g. 124, 126, 128, 130, 224, 226, 228, or 266), the isolation region (e.g. 240 or 270) is configured to contain a plurality of micro-objects. In other embodiments, the isolation region can be configured to contain only one, two, three, four, five, or a similar relatively small number of micro-objects. Accordingly, the volume of an isolation region can be, for example, at least 1×106, 2×106, 4×106, 6×106 cubic microns, or more.
In various embodiments of sequestration pens, the width Wch of the channel (e.g., 122) at a proximal opening (e.g. 234) can be within any of the following ranges: about 50-1000 microns, 50-500 microns, 50-400 microns, 50-300 microns, 50-250 microns, 50-200 microns, 50-150 microns, 50-100 microns, 70-500 microns, 70-400 microns, 70-300 microns, 70-250 microns, 70-200 microns, 70-150 microns, 90-400 microns, 90-300 microns, 90-250 microns, 90-200 microns, 90-150 microns, 100-300 microns, 100-250 microns, 100-200 microns, 100-150 microns, and 100-120 microns. In some other embodiments, the width Wch of the channel (e.g., 122) at a proximal opening (e.g. 234) can be in a range of about 200-800 microns, 200-700 microns, or 200-600 microns. The foregoing are examples only, and the width Wch of the channel 122 can be in other ranges (e.g., a range defined by any of the endpoints listed above). Moreover, the Wch of the channel 122 can be selected to be in any of these ranges in regions of the channel other than at a proximal opening of a sequestration pen.
In some embodiments, a sequestration pen has a height of about 30 to about 200 microns, or about 50 to about 150 microns. In some embodiments, the sequestration pen has a cross-sectional area of about 1×104-3×106 square microns, 2×104-2×106 square microns, 4×104-1×106 square microns, 2×104-5×105 square microns, 2×104-1×105 square microns or about 2×105-2×106 square microns. In some embodiments, the connection region has a cross-sectional width of about 100 to about 500 microns, 200 to about 400 microns or about 200 to about 300 microns.
In various embodiments of sequestration pens, the height Hch of the channel (e.g., 122) at a proximal opening (e.g., 234) can be within any of the following ranges: 20-100 microns, 20-90 microns, 20-80 microns, 20-70 microns, 20-60 microns, 20-50 microns, 30-100 microns, 30-90 microns, 30-80 microns, 30-70 microns, 30-60 microns, 30-50 microns, 40-100 microns, 40-90 microns, 40-80 microns, 40-70 microns, 40-60 microns, or 40-50 microns. The foregoing are examples only, and the height Hch of the channel (e.g., 122) can be in other ranges (e.g., a range defined by any of the endpoints listed above). The height Hch of the channel 122 can be selected to be in any of these ranges in regions of the channel other than at a proximal opening of a sequestration pen.
In various embodiments of sequestration pens a cross-sectional area of the channel (e.g., 122) at a proximal opening (e.g., 234) can be within any of the following ranges: 500-50,000 square microns, 500-40,000 square microns, 500-30,000 square microns, 500-25,000 square microns, 500-20,000 square microns, 500-15,000 square microns, 500-10,000 square microns, 500-7,500 square microns, 500-5,000 square microns, 1,000-25,000 square microns, 1,000-20,000 square microns, 1,000-15,000 square microns, 1,000-10,000 square microns, 1,000-7,500 square microns, 1,000-5,000 square microns, 2,000-20,000 square microns, 2,000-15,000 square microns, 2,000-10,000 square microns, 2,000-7,500 square microns, 2,000-6,000 square microns, 3,000-20,000 square microns, 3,000-15,000 square microns, 3,000-10,000 square microns, 3,000-7,500 square microns, or 3,000 to 6,000 square microns. The foregoing are examples only, and the cross-sectional area of the channel (e.g., 122) at a proximal opening (e.g., 234) can be in other ranges (e.g., a range defined by any of the endpoints listed above).
In various embodiments of sequestration pens, the length Lon of the connection region (e.g., 236) can be in any of the following ranges: about 1-600 microns, 5-550 microns, 10-500 microns, 15-400 microns, 20-300 microns, 20-500 microns, 40-400 microns, 60-300 microns, 80-200 microns, or about 100-150 microns. The foregoing are examples only, and length Lcon of a connection region (e.g., 236) can be in a different range than the foregoing examples (e.g., a range defined by any of the endpoints listed above).
In various embodiments of sequestration pens the width Wcon of a connection region (e.g., 236) at a proximal opening (e.g., 234) can be in any of the following ranges: 20-500 microns, 20-400 microns, 20-300 microns, 20-200 microns, 20-150 microns, 20-100 microns, 20-80 microns, 20-60 microns, 30-400 microns, 30-300 microns, 30-200 microns, 30-150 microns, 30-100 microns, 30-80 microns, 30-60 microns, 40-300 microns, 40-200 microns, 40-150 microns, 40-100 microns, 40-80 microns, 40-60 microns, 50-250 microns, 50-200 microns, 50-150 microns, 50-100 microns, 50-80 microns, 60-200 microns, 60-150 microns, 60-100 microns, 60-80 microns, 70-150 microns, 70-100 microns, and 80-100 microns. The foregoing are examples only, and the width Wcon of a connection region (e.g., 236) at a proximal opening (e.g., 234) can be different than the foregoing examples (e.g., a range defined by any of the endpoints listed above).
In various embodiments of sequestration pens, the width Wcon of a connection region (e.g., 236) at a proximal opening (e.g., 234) can be at least as largest dimension of a micro-object (e.g., biological cell which may be a T cell, B cell, or an ovum or embryo) that the sequestration pen is intended for. For example, the width Wcon of a connection region 236 at a proximal opening 234 of an sequestration pen that a droplet will be placed into can be in any of the following ranges: about 100 microns, about 110 microns, about 120 microns, about 130 microns, about 140 microns, about 150 microns, about 160 microns, about 170 microns, about 180 microns, about 190 microns, about 200 microns, about 225 microns, about 250 microns, about 300 microns or about 100-400 microns, about 120-350 microns, about 140-200-200 300 microns, or about 140-200 microns. The foregoing are examples only, and the width Wcon of a connection region (e.g., 236) at a proximal opening (e.g., 234) can be different than the foregoing examples (e.g., a range defined by any of the endpoints listed above).
In various embodiments of sequestration pens, the width Wpr of a proximal opening of a connection region may be at least as large as the largest dimension of a micro-object (e.g., a biological micro-object such as a cell) that the sequestration pen is intended for. For example, the width Wpr may be about 50 microns, about 60 microns, about 100 microns, about 200 microns, about 300 microns or may be in a range of about 50-300 microns, about 50-200 microns, about 50 -100 microns, about 75-150 microns, about 75-100 microns, or about 200-300 microns.
In various embodiments of sequestration pens, a ratio of the length Lcon of a connection region (e.g., 236) to a width Warn of the connection region (e.g., 236) at the proximal opening 234 can be greater than or equal to any of the following ratios: 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, or more. The foregoing are examples only, and the ratio of the length Lcon of a connection region 236 to a width Warn of the connection region 236 at the proximal opening 234 can be different than the foregoing examples.
In various embodiments of microfluidic devices 100, 200, 230, 250, 280, 290, 320, 600, 700 Vmax can be set around 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, or 1.5 μL/sec.
In various embodiments of microfluidic devices having sequestration pens, the volume of an isolation region (e.g., 240) of a sequestration pen can be, for example, at least 5×105, 8×105, 1×106, 2×106, 4×106, 6×106, 8×106, 1×107, 5×107, 1×108, 5×108, or 8×108 cubic microns, or more. In various embodiments of microfluidic devices having sequestration pens, the volume of a sequestration pen may be about 5×105, 6×105, 8×105, 1×106, 2×106, 4×106, 8×106, 1×107, 3×107, 5×107, or about 8×107 cubic microns, or more. In some other embodiments, the volume of a sequestration pen may be about 1 nanoliter to about 50 nanoliters, 2 nanoliters to about 25 nanoliters, 2 nanoliters to about 20 nanoliters, about 2 nanoliters to about 15 nanoliters, or about 2 nanoliters to about 10 nanoliters.
In various embodiment, the microfluidic device has sequestration pens configured as in any of the embodiments discussed herein where the microfluidic device has about 5 to about 10 sequestration pens, about 10 to about 50 sequestration pens, about 100 to about 500 sequestration pens; about 200 to about 1000 sequestration pens, about 500 to about 1500 sequestration pens, about 1000 to about 2000 sequestration pens, or about 1000 to about 3500 sequestration pens. The sequestration pens need not all be the same size and may include a variety of configurations (e.g., different widths, different features within the sequestration pen.
In some other embodiments, the microfluidic device has sequestration pens configured as in any of the embodiments discussed herein where the microfluidic device has about 1500 to about 3000 sequestration pens, about 2000 to about 3500 sequestration pens, about 2500 to about 4000 sequestration pens about 3000 to about 4500 sequestration pens, about 3500 to about 5000 sequestration pens, about 4000 to about 5500 sequestration pens, about 4500 to about 6000 sequestration pens, about 5000 to about 6500 sequestration pens, about 5500 to about 7000 sequestration pens, about 6000 to about 7500 sequestration pens, about 6500 to about 8000 sequestration pens, about 7000 to about 8500 sequestration pens, about 7500 to about 9000 sequestration pens, about 8000 to about 9500 sequestration pens, about 8500 to about 10,000 sequestration pens, about 9000 to about 10,500 sequestration pens, about 9500 to about 11,000 sequestration pens, about 10,000 to about 11,500 sequestration pens, about 10,500 to about 12,000 sequestration pens, about 11,000 to about 12,500 sequestration pens, about 11,500 to about 13,000 sequestration pens, about 12,000 to about 13,500 sequestration pens, about 12,500 to about 14,000 sequestration pens, about 13,000 to about 14,500 sequestration pens, about 13,500 to about 15,000 sequestration pens, about 14,000 to about 15,500 sequestration pens, about 14,500 to about 16,000 sequestration pens, about 15,000 to about 16,500 sequestration pens, about 15,500 to about 17,000 sequestration pens, about 16,000 to about 17,500 sequestration pens, about 16,500 to about 18,000 sequestration pens, about 17,000 to about 18,500 sequestration pens, about 17,500 to about 19,000 sequestration pens, about 18,000 to about 19,500 sequestration pens, about 18,500 to about 20,000 sequestration pens, about 19,000 to about 20,500 sequestration pens, about 19,500 to about 21,000 sequestration pens, or about 20,000 to about 21,500 sequestration pens.
In some embodiments, the chamber (or sequestration pen) can include a holding region (e.g., isolation region) configured to hold a liquid droplet, and one (or more) connection region that fluidically connects the holding region to the microfluidic channel. A first connection region can be configured to allow movement of the liquid droplet between the microfluidic channel and the chamber. When a second connection region is present, it can be configured to allow for fluid flow and pressure relief when a liquid droplet is moved between the microfluidic channel and the holding region. In some embodiments, the enclosure can further include a second microfluidic channel. In such embodiments, the chamber can be connected to both the first microfluidic channel and the second microfluidic channel.
In some embodiments, the microfluidic channel(s) can have a height of about 30 to about 200 microns, or about 50 to about 150 microns, with the height measured in a direction normal to the direction of fluid flow through the channel. In some embodiments, the microfluidic channel(s) has a width of about 50 to about 1000 microns, or about 100 to about 500 microns, with the width measured in a direction normal to the direction of fluid flow through the channel.
In some embodiments, the chamber (or sequestration pen) has a height that is substantially the same as the height of the microfluidic channel(s). For example, the chamber height can be about 30 to about 200 microns, or about 50 to about 150 microns. In some embodiments, the chamber (or holding pen) has a cross-sectional area of about 100,000 to about 2,500,000 square microns, or about 200,000 to about 2,000,000 square microns. In some embodiments, the connection region (first, second, etc.) has a height that is substantially the same as the height of the corresponding chamber and/or the microfluidic channel off of which the connection regions opens. In some embodiments, the connection region has a width of about 50 to about 500 microns, or about 100 to about 300 microns.
In some embodiments, the microfluidic device includes a culture chamber (e.g., a sequestration pen) suitable for culturing biological micro-objects. The culture chamber can be located within the enclosure, and can be is connected to a microfluidic channel. When the culture chamber is located within the enclosure, the enclosure can include a perfusion microfluidic channel configured to flow fresh culture medium past the culture chamber such that nutrients in the fresh culture medium and waste products in the culture chamber can be exchanged (e.g., by diffusion of nutrients into the culture chamber and diffusion of waste products out into the culture medium). The perfusion channel can be separate from the microfluidic channel connected to the droplet generator.
H. Surface Modification.
Surfaces of materials, devices, and/or apparatuses for manipulation and storage of biomaterials may have native properties that are not optimized for short and/or long term contact with such material, which may include but is not limited to micro-objects (including but not limited to biological micro-objects such as biological cells), biomolecules, fragments of the biomolecules or biological micro-objects, and any combination thereof. It may be useful to modify one or more surfaces of a material, device or apparatus to decrease one or more undesired phenomena associated with a native surface in contact with one or more biomaterials. In other embodiments, it may be useful to enhance surface properties of the material, device, and/or apparatus to introduce a desired characteristic to the surface, thereby broadening the handling, manipulation or processing capabilities of the material, device, and/or apparatus. To that end, molecules which can modify a surface to either decrease undesired properties or introduce desirable properties are needed.
1. Compounds useful for Modification of Surfaces.
In various embodiments, a surface modifying compound may include a surface modifying ligand which may be a non-polymeric moiety such as an alkyl moiety or a substituted alkyl moiety, such as a fluoroalkyl moiety (including but not limited to a perfluoroalkyl moiety) which covalently modifies the surface to which it is attached. The surface modifying compound also includes a connecting moiety, which is the group which covalently attaches the surface modifying ligand to the surface, as shown schematically in Equation 1. The covalently modified surface has the surface modifying ligand attached via a linking group, which is the product of the reaction of the connecting moiety with functional groups of the surface (including hydroxide, oxide, amine or sulfur).
In some embodiments, the surface modifying compound may include carbon atoms forming a linear chain (e.g., a linear chain of at least 10 carbons, or at least 14, 16, 18, 20, 22, or more carbons) and may be an unbranched alkyl moiety. In some embodiments, the alkyl group may include a substituted alkyl group (e.g., some of the carbons in the alkyl group can be fluorinated or perfluorinated). In some embodiments, the alkyl group may include a first segment, which may include a perfluoroalkyl group, joined to a second segment, which may include a non-substituted alkyl group, where the first and second segments may be joined directly or indirectly (e.g., by means of an ether linkage). The first segment of the alkyl group may be located distal to the linking group, and the second segment of the alkyl group may be located proximal to the connecting moiety.
In various embodiments, the surface modifying compound may have a structure of Formula I:
wherein a connecting moiety V is —P(O)(OH)Q- or —Si(T)2W; W is -T, —SH, or —NH2 and is the moiety configured to connect to the surface; Q is —OH and is the moiety configured to connect to the surface; and T is OH, OC1-3alkyl, or Cl. R is hydrogen or fluorine and M is hydrogen or fluorine. Each instance of h is 0 or an integer of 2 or 3; j is 0 or 1; k is 0 or is 1; m is 0 or an integer of 1 to 25; and n is 0 or an integer of 1 to 25. In some other embodiments, the sum of (n+[(h+j)·k]+m) may be an integer of 11 to 25. In some embodiments, M is hydrogen. In various embodiments, m is 2. In some embodiments, k is 0. In other embodiments, k is 1. In various embodiments, j is 1. For the compound of Formula I, when k is an integer of 1, then m may be at least 2 and M is hydrogen. For the compound of Formula I, when k is 0 and R is fluorine, then m may be at least 2 and M is hydrogen.
In various embodiments, where the surface modifying compound has a structure of Formula I, the connecting moiety V may be —Si(T)2W, where T and W are defined as above. W may be OC1-3alkyl, or Cl. W may be methoxy, ethoxy or propoxy. In some embodiments, W may be methoxy. T may be may be OC1-3alkyl, or Cl. In various embodiments, connecting moiety V is —Si(OMe)3. In various other embodiments, V may be —P(O)(OH)Q, where Q is OH.
The surface modifying compound of Formula 1 may have a preferred range of number of atoms making up the linear backbone of the compound. As defined above each of the segments that make up the compound of Formula 1 may have a range of sizes. Accordingly, a compound of Formula 1 may have repeating units as defined above such that (n+[(h+j)·k]+m) is equal to 25, which would yield a total length of 26 atoms, including the terminal CR3-group, attached to the connecting moiety. In the instance of (n+[(h+j)·k]+m) equal to 25, a variety of different compositions can be encompassed. For instance, the segment —[CR2]n— may have n=23; —[(CH2)h—(O)j]k— may have k=0; and —[CM2]m- may have m=2. Another instance having the same total (n+[(h+j)·k]+m) equal to 25, may have segment —[CR2]n- where n=6; —[(CH2)h—(O)j]k— where k=3, and includes j=1 and h=2; and —[CM2]m- may have m=4.
In some embodiments, the sum of (n+[(h+j)·k]+m) may be 11, 13, 15, 17, or 21. In other embodiments, the sum of (n+[(h+j)·k]+m) may be 15 or 17. In yet other embodiments, the sum of (n+[(h+j)·k]+m) may be 13 or 15.
In some embodiments, one or more ether linkages may be present in the compound of Formula I. In some embodiments, j may be 1. In some embodiments, where k and j are both 1, m may be at least two. In some embodiments, where k and j are both 1, h may be 0.
In yet other embodiments, backbone carbons may be fluorinated. In some embodiments, backbone carbons may be perfluorinated, where each R of CR3—, and/ or —[CR2]n— and/or —[CM2]m- may be fluorinated. In some embodiments, a section of the compound may have carbon backbone atoms that are fluorinated and other sections of the compound may have carbon backbone atom that are substituted with hydrogen. For example, in some embodiments, CR3— and —[CR2]n— segments may have fluorine nonbackbone substituents (e.g., R is fluorine) while —[CM]m- segments may have hydrogen nonbackbone substituents (e.g., M is hydrogen). In some embodiments, when R is fluorine, then k is 0. In other embodiments, R may be fluorine and k is 1, j is 1 and h is 2. In various embodiments, M may be hydrogen.
In yet other embodiments, the compound of Formula 1 may be synthesized from hydrosilation of an olefin as described below, where m is at least two and M is hydrogen. In some embodiments, m is 2 and M is hydrogen.
Some of the variety of compounds of Formula I may be more readily seen in subsets of compounds described in the following formulae, but these formulae are in no way limiting to the breadth of Formula I.
In some embodiments, the compound of Formula I may include a compound of Formula 110:
CH3(CH2)mSi(OC1-3alkyl)3 ; Formula 110
where m is an integer of 9 to 23. In some embodiments, m may be 11, 13, 15, 17, or 19. In some other embodiments m may be 13 or 15.
In other embodiments, the compound of Formula I may include a compound of Formula 111:
CF3(CF2)n(CH2)2Si(OC1-3alkyl)3; Formula 111
where n may be an integer of 9 to 22. Alternatively, n may be an integer of 11 to 17. In some other embodiments, n may be 9, 11, 13, or 15. In some embodiments, n may be 13 or 15.
In yet other embodiments, the compound of Formula I may include a compound of Formula 112:
CR3(CR2)n(CH2(h(CH2)mSi(OC1-3alkyl)3; Formula 112
where n is an integer of 3 to 19; his an integer of 2 or 3; and m is an integer of 2 to 18. In some embodiments, R may be fluorine. In some embodiments n may be an integer of 3 to 11, h may be 2, and m may be an integer of 2 to 15.
Alternatively, the compound of Formula I may include a compound of Formula 113:
CR3(CR2)n (CM2)mP (O)(OH)2; Formula 113
where n is an integer of 3 to 21; and m is an integer of 2 to 21. In some embodiments of the compound of Formula 113, R may be fluorine. In some embodiments, M may be hydrogen. In various embodiments, n may be 5, 7, 9, or 11. In other embodiments, m may be 2, 4, 5, 7, 9, 11 or 13.
2. Surfaces for Modification.
A surface capable of being modified by the surface modifying compounds described herein, including a compound of Formula I, may be a metal, metal oxide, glass or polymer. Some materials that may have a covalently modified surface introduced therein in may include but not be limited to silicon and its oxides, silicones, aluminum or its oxide thereof (Al2O3), Indium Tantalum Oxide (ITO), titanium dioxide (TiO2), zirconium oxide (ZrO2), hafnium(IV) oxide (HfO2), tantalum (V) oxide (Ta2O5), or any combination thereof. The surface may be a wafer or sheet of these materials, or may be incorporated within an apparatus or device. In some embodiments, the surface including any of these materials may be incorporated within a microfluidic device as described herein.
Polymers may include any suitable polymer. A suitable polymer may include but is not limited to (e.g. rubber, plastic, elastomer, silicone, organosilicone, such as polydimethylsiloxane (“PDMS”), or the like), which can be gas permeable. Other examples can include molded glass, a patternable material such as a silicone polymer (e.g. photo-patternable silicone or “PPS”), photo-resist (e.g., an epoxy-based photo-resist such as SU8), or the like. In other embodiments, a surface of a material such as a natural fiber or wood may be functionalized by the surface modifying compounds described herein, including a compound of Formula I, to introduce a covalently modified surface.
The surface to be modified may include a nucleophilic moiety including but not limited to hydroxide, amino and thiol. The nucleophilic moiety (e.g., hydroxide (in some embodiments referred to as oxide)) on the surface may react with the surface modifying compounds described herein, including a compound of Formula I, to covalently link the surface modifying ligand to the surface, via a siloxy linking group or phosphonate linking group, to provide the functionalized surface. The surface to be modified may include native nucleophilic moieties, or may be treated with reagents (e.g., piranha solution) or by plasma treatment to introduce nucleophilic moieties (e.g., hydroxide (alternatively referred to as oxide)).
In some embodiments, the surface may be formed from any of the above materials, singly or in any combination. The surface may include a semiconductor substrate. In various embodiments, the surface including a semiconductor substrate may further include a DEP or EW substrate as described herein. In some embodiments, the surface including a semiconductor substrate having a DEP or EW substrate may be part of a microfluidic device as described herein.
In some embodiments, the modified surface may be at least one inward-facing surface of a microfluidic device as described herein. The at least one surface may be part of the flow region of the microfluidic device (which may include a channel) or may include a surface of an enclosed structure such as a pen, which may include a sequestration pen as described herein.
3. Covalently Modified Surface.
A covalently modified surface may include a surface modifying ligand, which may be a non-polymeric moiety such as an alkyl moiety, a substituted alkyl moiety, such as a fluoroalkyl moiety (including but not limited to a perfluoroalkyl moiety) and may be any surface modifying ligand described above, which is covalently bound to the surface via a linking group, which is the moiety resultant from reaction of the connecting moiety with the surface. The linking group may be a siloxy linking group or a phosphonate linking group. Siloxy and phosphonate linking groups are also referred to herein as siloxane and phosphonic acid linking groups, respectively.
In some embodiments, the surface modifying ligand may include carbon atoms forming a linear chain (e.g., a linear chain of at least 10 carbons, or at least 14, 16, 18, 20, 22, or more carbons) and may be an unbranched alkyl moiety. In some embodiments, the alkyl group may include a substituted alkyl group (e.g., some of the carbons in the alkyl group can be fluorinated or perfluorinated). In some embodiments, the alkyl group may include a first segment, which may include a perfluoroalkyl group, joined to a second segment, which may include a non-substituted alkyl group, where the first and second segments may be joined directly or indirectly (e.g., by means of an ether linkage). The first segment of the alkyl group may be located distal to the linking group, and the second segment of the alkyl group may be located proximal to the linking group.
In some embodiments, a covalently modified surface has a structure of Formula II:
wherein is the surface; V is —P(O)(OY)W— or —Si(OZ)2W. W is —O—, —S—, or —NH— and connects to the surface. Z is a bond to an adjacent silicon atom attached to the surface or is a bond to the surface. Y is a bond to an adjacent phosphorus atom attached to the surface or is a bond to the surface. For the covalently modified surface of Formula II, R, M, h, j, k, m, and n are as defined above for Formula I. When k is an integer of 1, then m is at least 2 and M is hydrogen. When k is 0 and R is fluorine, then m is at least 2 and M is hydrogen. The covalently modified surface of Formula II can be described as a surface modifying ligand attached via a linking group LG, as in Formula IIA, where LG is linked to the surface:
The covalently modified surface may include any surface of Formula II, in any combination, as described above for the surface modifying compound of Formula I.
In some embodiments, the covalently modified surface of Formula II may be a surface of Formula 210:
wherein is the surface, oxygen attached to the silicon atom is also bound to the surface, and m is an integer of 11 to 23. In some embodiments, m may be 11, 13, 15, 17, or 19. In some other embodiments m may be 13 or 15.
In some other embodiments, the covalently modified surface of Formula II may be a surface of Formula 211:
wherein is the surface, oxygen attached to the silicon atom is also bound to the surface, and n may be an integer of 9 to 22. Alternatively, n may be an integer of 11 to 17. In some other embodiments, n may be 7, 9, 11, 13, or 15. In some embodiments, n may be 13 or 15.
In yet other embodiments, the covalently modified surface of Formula II may be a surface of Formula 212:
wherein is the surface, oxygen attached to the silicon atom is also bound to the surface, and n is an integer of 3 to 21, his an integer of 2 or 3, and m is an integer of 2 to 21. In some embodiments, R may be fluorine. In some embodiments, n may be an integer of 3 to 11, h may be 2, and m may be an integer of 2 to 15.
Alternatively, the covalently modified surface of Formula II may be a surface of Formula 213:
wherein is the surface, oxygen attached to the phosphorus atom is also bound to the surface, n is an integer of 3 to 21 and m is an integer of 2 to 21. In some embodiments of the compound of Formula 113, R may be fluorine. In some embodiments, M may be hydrogen. In various embodiments, n may be 5, 7, 9, or 11. In other embodiments, m may be 2, 4, 5, 7, 9, 11 or 13.
In some embodiments, the microfluidic device comprises a flow region fluidically connected to a first inlet and a first outlet, the flow region configured to contain a flow of a first fluidic medium. The microfluidic device may include one or more chambers opening to the flow region. The covalently modified surface may be a covalently modified substrate of the microfluidic device and may underlay the flow region and/or at least one chamber. In some embodiments, all or substantially all the interior surfaces of the microfluidic device configured to face fluid have a covalently modified surface of Formula II.
In some embodiments, the microfluidic device comprises a droplet actuation surface comprising a hydrophobic layer which is covalently bonded to a dielectric layer of the device. In some embodiments, the hydrophobic layer is a monolayer. In some embodiments, the hydrophobic layer is a monolayer comprising a surface modifying ligand and a linking group that links the surface modifying ligand to the surface.
In some embodiments, the outer hydrophobic layer of the substrate has a thickness of less than 5 nanometers (e.g., about 1.5 to 3.0 nanometers). In some embodiments, the outer hydrophobic layer of the substrate can be patterned such that select regions are relatively hydrophilic compared to the remainder of the outer hydrophobic layer.
In some embodiments, the outer hydrophobic layer comprises self-associating molecules covalently bonded to the inner dielectric layer (e.g., through a linker) so as to form a densely-packed hydrophobic monolayer. In some embodiments, the self-associating molecules of the hydrophobic monolayer each comprise a siloxane group (e.g., as part of the linker). For example, the siloxane group can have the formula —Si(OZ)2W— wherein W is —O—, —S—, or —NH— and connects to the surface; and Z is a bond to an adjacent silicon atom attached to the surface (such as through another W bonded directly to the silicon) or is a bond to the surface. In other embodiments, the self-associating molecules of the hydrophobic monolayer each comprise a phosphonic acid group (e.g., as part of the linker). For example, the phosphonic acid group can have the formula —P(O) (OY)W— wherein W is —O—, —S—, or —NH— and connects to the surface; and Y is a bond to an adjacent phosphorus atom attached to the surface (such as through another W bonded directly to the phosphorus) or is a bond to the surface. The siloxane groups or the phosphonic acid groups can be covalently bonded to the surface of the inner dielectric layer, e.g., through an oxygen. In some embodiments, the self-associating molecules of the hydrophobic monolayer each comprise a surface modifying ligand and a linking group that links, either directly or indirectly, the surface modifying ligand to the surface of the inner dielectric layer. The surface modifying ligand can be any surface modifying ligand disclosed herein. For example, the surface modifying ligand can comprise an aliphatic group, such as an alkane group. Thus, for example, the self-associating molecules of the hydrophobic monolayer can be alkyl-terminated siloxane or alkyl-terminated phosphonic acid molecules. The alkyl groups can include a chain (e.g., an unbranched chain) of at least 10 carbons (e.g., at least 12, 14, 16, 18, 20, 22, or more carbons). In other embodiments, the surface modifying ligand can comprise a fluorine-substituted aliphatic group, such as a fluoroalkyl group. Thus, for example, the self-associating molecules can be fluoroalkyl-terminated siloxane or fluoroalkyl-terminated phosphonic acid molecules. The fluoroalkyl groups can include a chain (e.g., an unbranched chain) of at least 10 carbons (e.g., at least 12, 14, 16, 18, 20, 22, or more carbons). In certain embodiments, the fluoroalkyl groups include one or more (e.g., at least 4, 5, 6, 7, 8, 9, 10, 11, 12, or more) perfluorinated carbons. For example, the fluoroalkyl groups can have the chemical formula CF3-(CF2)m—(CH2)n—, wherein m is at least 2, n is at least 2, and m+n is at least 9. In some embodiments, the surface modifying ligand comprises an ether linkage between a first aliphatic group and a second aliphatic group. For example, the first aliphatic group can be an alkyl group and the second aliphatic group can be a fluoroalkyl group (e.g., a perfluoroalkyl group). In certain embodiments, the alkyl or fluoroalkyl group of the surface modifying ligand is unbranched. In some embodiments, the alkyl or fluoroalkyl group of the surface modifying ligand does not contain any cyclic structures.
The surface may be modified with covalently bound molecules having (i) a linker (e.g., as described above) and (ii) an unbranched alkane group (i.e., —(CH2)n—CH3, where n=9 or greater, e.g., 11 or 15 or greater). In another aspect, a surface of the chip may be modified with covalently bound molecules having (i) a linker (e.g., as described above), (ii) a short unbranched alkane, and (iii) a perfluoroalkane group (i.e., —(CH2)n-(CF2)m-CF3, wherein n=2 or greater and m=5 or greater, e.g., 7, 9, 11, 13 or greater). In some embodiments, the combination of the short unbranched alkane and the perfluoroalkane group is —(CH2)2—(CF2)13—CF3. In some embodiments, the unbranched alkane group is C18 group (i.e., —(CH2)17—CH3). The linker may be a siloxane (e.g., —Si(OZ)2—O—, where Z is bound to an adjacent Si atom or the surface) or a phosphonic acid (e.g., —P(O)(OY)—, where Y is bound to an adjacent P atom or the surface). In one embodiment, the linker is a siloxane linker.
In some embodiments, the hydrophobic layer is a monolayer comprising a surface modifying ligand and a linking group that links the surface modifying ligand to the surface, having a structure of:
where is the surface, V is a linker, m is an integer of 9 or 11 or greater (“SSRL1 coating” hereafter). In some embodiments, V is —Si(OZ)2W—; W is —O— and connects to the surface; and Z is a bond to an adjacent silicon atom attached to the surface or is a bond to the surface. Alternatively, W can be —O—, —S—, or —NH—. In some embodiments, V is —P(O)(OY)W—; W is —O— and connects to the surface; Y is a bond to an adjacent phosphorus atom attached to the surface or is a bond to the surface. Alternatively, W can be —O—, —S—, or —NH—. In some embodiments, m is an integer of 15 or greater. In some embodiments, m ranges from 12 to 25, 12 to 21, 15 to 25, 15 to 21, 15 to 19, or 16 to 18. In some embodiments, m is 15, 17 or 19. In some embodiments, m is 17.
In some embodiments, the hydrophobic layer is a monolayer comprising a surface modifying ligand and a linking group that links the surface modifying ligand to the surface, having a structure of:
where is the surface, V is a linker, n+m+j is 13 or greater, n is at least 5, m is 2 or greater, and j is 0 or 1 (“SSRL2 coating” hereafter). In some embodiments, V is —Si(OZ)2W—; W is —O— and connects to the surface; and Z is a bond to an adjacent silicon atom attached to the surface or is a bond to the surface. Alternatively, W can be —O—, —S—, or —NH—. In some embodiments, V is —P(O)(OY)W—; W is —O— and connects to the surface; Y is a bond to an adjacent phosphorus atom attached to the surface or is a bond to the surface. Alternatively, W can be —O—, —S—, or —NH—. In some embodiments, n is at least 7, at least 9, at least 11, at least 13, or greater. In some embodiments, m ranges from 2 to 13, 2 to 10, 2 to 8, 2 to 6, or 2 to 4. In some embodiments, m is 2. In some embodiments, wherein n is 11 or 13.
In the embodiment shown in
4. Native Surface.
The at least one surface of the microfluidic device to be modified may be glass, metal, metal oxide or polymer. Some materials that may be incorporated within the microfluidic device and may be modified to have a covalently modified surface of Formula II introduced therein in may include but not be limited to silicon and its oxides, silicones, aluminum or its oxide thereof (Al2O3), Indium Tantalum Oxide (ITO), titanium dioxide (TiO2), zirconium oxide (ZrO2), hafnium(IV) oxide (HfO2), tantalum (V) oxide (Ta2O5), or any combination thereof. Polymers may include any suitable polymer. A suitable polymer may include but is not limited to (e.g. rubber, plastic, elastomer, silicone, organosilicone, such as polydimethylsiloxane (“PDMS”), or the like), which can be gas permeable. Other examples can include molded glass, a patternable material such as a silicone polymer (e.g. photo-patternable silicone or “PPS”), photo-resist (e.g., an epoxy-based photo-resist such as SU8), or the like.
5. Physical and Performance Properties of the Covalently Modified Surface.
In some embodiments, the covalently modified surface may have increased hydrophobic character. The increased hydrophobic character of the modified surface may prevent fouling by biomaterials. Surface fouling, as used herein, refers to the amount of material indiscriminately deposited on the surface of the microfluidic device, which may include permanent or semi-permanent deposition of biomaterials such as protein and degradation products, nucleic acids, and respective degradation products. Such fouling can increase the amount of adhesion of biological micro-objects to the surface. In other embodiments, increased hydrophobic character of a covalently modified surface may decrease adhesion of biological micro-objects on the surface, independently of adhesion initiated by surface fouling.
Modification of the surface may increase the durability, functionality, and/or biocompatibility of the surface. Each of these characteristics may further benefit the viability (including growth rate and/or cell doubling rate), nature of the colony formed upon a covalently modified surface as described herein, including a surface having a structure of Formula II, or portability (including viability upon export) of micro-objects or biomolecules upon the modified surface and within devices and/or apparatuses having a covalently modified surface.
In some embodiments, the covalently modified surface, which may be any surface as described herein, including a surface of Formula II, may have a thickness of less than 10 nm (e.g., less than about 7 nm, less than about 5 nm, or about 1.5 to 3.0 nm). This may provide an advantageously thin layer on the modified surface, particularly in contrast with other hydrophobic materials such as CYTOP®, a perfluoro tetrahydrofuranyl polymer which is spin-coated yielding a typical thickness of about 30 to 50 nm. Data shown in Table 1 is for a silicon/silicon oxide surface which is treated to have a covalently modified surface as shown in the table. Contact angle measurements were obtained using the static sessile drop method. (Drelich, J. Colloid Interface Sci. 179, 37-50, 1996.) Thickness was measured by ellipsometry.
Contact angle hysteresis measurements were performed using a Biotin Scientific contact angle goniometer. Chemically modified OEW surfaces were placed in a bath of 5 cSt silicone oil encased in a transparent holder. A phosphate buffered saline (PBS) droplet was then dispensed onto the surface in the oil. A platinum (Pt) wire electrode was inserted into the droplet, and the sessile water contact angle was measured. Next, an applied AC voltage of 50 Vppk at 30 kHz frequency was applied between the OEW substrate and the Pt wire inserted into the PBS droplet for 10 seconds. Next, the applied voltage was removed, and the contact angle was measured again. The contact angle hysteresis was calculated by subtracting the contact angle at zero bias after applying the 50Vppk AC voltage from the original contact angle at zero bias before applying the voltage.
T and Q are as described above.
The contact angles observed for modified surfaces are in contrast to the contact angle for water on a plasma cleaned silicon surface of less than 10 degrees. Each of these surfaces is less wettable than that of the native silicon/silicon oxide surface.
Other analytical methods suitable to characterize the surface can include infrared spectroscopy and/or X-ray photoelectron spectroscopy.
Another desirable characteristic of the modified surfaces of the disclosure is a lack of autofluorescence, which can be dependent upon the chemical nature of the surface modifying compound.
In some embodiments, the covalently modified surface described herein, including a surface of Formula II, may form a monolayer. The uniformity and evenness of a monolayer modified surface may provide advantageous performance, particularly if the monolayer modified surface has other functional attributes. For example, the covalently modified surface described herein, including a surface of Formula II, may also include an electrode activation substrate, and optionally further may include a dielectric layer, as may be found in materials, devices and/or apparatuses having a dielectrophoresis configuration or an electrowetting configuration. The lack of unsaturation of the perfluoroalkyl moieties of the modified surface can minimize “charge trapping” compared to a monolayer containing, for example olefinic or aromatic moieties. Additionally, the densely packed nature of the monolayer formed in the surface described herein, including a surface of Formula II, may minimize the potential for cations to be driven through the monolayer to the underlying metal, metal oxide, glass or polymer substrate. Without being limited by theory, the disruption of the substrate surface by addition of cations to substrate composition may disrupt the electrical properties of the substrate, thereby reducing its ability to function electrokinetically.
Further, the ability to introduce the modified surface via a covalent linkage may increase the dielectric strength of the modified surface and protect the underlying material from breakdown under application of an electric field. The uniformity and thinness of an dielectrophoretic or electrowetting surface of a material, device and/or apparatus having a covalently modified surface described herein, including a surface of Formula II, may further provide advantageous benefit for such modified dielectrophoretic and/or electrowetting surface when the material, device and/or apparatus is optically actuated.
6. Methods of Preparation of the Covalently Modified Surface.
A surface of a material that may be used as a component of a device or apparatus may be modified before assembly of the device or apparatus. Alternatively, partially or completely constructed device or apparatus may be modified such that all surfaces that will contact biomaterials including biomolecules and/or micro-objects (which may include biological micro-objects) are modified at the same time. In some embodiments, the entire interior of a device and/or apparatus may be modified, even if there are differing materials at different surfaces within the device and/or apparatus. In some embodiments, the partially or completely constructed device and/or apparatus may be a microfluidic device as described herein, or a component thereof.
The surface to be modified may be cleaned before modification to ensure that the nucleophilic moieties on the surface are freely available for reaction, e.g., not covered by oils or adhesives. Cleaning may be accomplished by any suitable method including treatment with solvents including alcohols or acetone, sonication, steam cleaning and the like. In some embodiments, the surface to be modified is treated with oxygen plasma treatment which removes contaminants, which at the same time, can introduce additional oxide (e.g., hydroxide) moieties on the surface. This can advantageously provide more sites for modification on the surface, thereby providing a more closely packed modified surface layer.
The surface to be modified may be cleaned before modification to ensure that the nucleophilic moieties on the surface are freely available for reaction, e.g., not covered by oils or adhesives. Cleaning may be accomplished by any suitable method including treatment with solvents including alcohols or acetone, sonication, steam cleaning and the like. In some embodiments, the surface to be modified is treated with oxygen plasma treatment which removes contaminants, which at the same time, can introduce additional oxide (e.g., hydroxide) moieties on the surface. This can advantageously provide more sites for modification on the surface, thereby providing a more closely packed modified surface layer.
In some embodiments, the method of covalently modifying a surface includes the steps of: contacting the surface with a compound of Formula I:
where V is —P(O)(OH)Q or —Si(T)2W. W is -T, —SH, or —NH2 and is the moiety configured to connect to the surface. Alternatively, when V is —P(O)(OH)Q, Q is —OH and is the moiety configured to connect to the surface. T is OH, OC1-13alkyl, or Cl. Each of R, M, h, j, k, m, and n are as defined above for the compound of Formula I. The sum of (n+[(h+j)·k]+m) is an integer of 11 to 25. In various embodiments, when k is an integer of 1, then m is at least 2 and M is hydrogen; and when k is 0 and R is fluorine, then m is at least 2 and M is hydrogen. The compound of Formula I reacts with a nucleophilic moiety of the surface; and the covalently modified surface is formed. Any combination or subcombination of the compound of Formula I may be used, as described above.
In various embodiments of the method, the covalent modified surface so formed may be a monolayer.
In some embodiments of the method, the compound of Formula I may be a compound of Formula 110:
CH3(CH2)mSi(OC1-3alkyl)3 ; Formula 110
where m is an integer of 9 to 23. In some embodiments, m may be 11, 13, 15, 17, or 19. In some other embodiments m may be 13 or 15.
In other embodiments of the method, the compound of Formula I may be a compound of Formula 111:
CF3(CF2)n(CH2)2Si(OC1-3alkyl)3; Formula 111
where n is an integer of 9 to 22. Alternatively, n may be an integer of 11 to 17. In other embodiments, n may be an integer of 11 to 17. In some other embodiments, n may be 9, 11, 13, or 15. In some embodiments, n may be 13 or 15.
In yet other embodiments of the method, the compound of Formula I may be a compound of Formula 112:
CR3(CR2)n(CH2)hO(CH2)mSi(OC1-3alkyl)3; Formula 112
where n is an integer of 3 to 21; his an integer of 2 or 3; and m is an integer of 2 to 21. In some embodiments, R may be fluorine. In some embodiments n may be an integer of 3 to 11, h may be 2, and m may be an integer of 2 to 15.
Alternatively, the surface may be contacted by a compound of Formula I which may be a compound of Formula 113:
CR3(CR2)n(CM2)mP(O)(OH)2; Formula 113
where n is an integer of 3 to 21; and m is an integer of 2 to 21. In some embodiments of the compound of Formula 113, R may be fluorine. In some embodiments, M may be hydrogen. In various embodiments, n may be 5, 7, 9, or 11. In other embodiments, m may be 2, 4, 5, 7, 9, 11 or 13.
The contacting step may be performed by contacting the surface with a liquid solution containing the compound of Formula I. For example, surfaces may be exposed to solutions containing 0.01 mM, 0.1 mM, 0.5 mM,1 mM, 10 mM, or 100 mM of the compound of Formula I. The reaction may be performed at ambient temperature and may be carried out for a period of time in the range of about 2h, 4h, 8h, 12 h, 18h, 24h, or any value in between. Examples of solvents include but are not limited to: toluene, 1,3 bistrifluorobenzene, or Fluorinert™ (3M) fluorinated solvents. An acid such as acetic acid may be added to the solution to increase the reaction rate by promoting hydrolysis of the trialkoxy groups, if present.
Alternatively, the surface may be contacted with a vapor phase containing the compound of Formula I. In some embodiments, when the reacting step is performed by contacting the surface with the compound of Formula I in the vapor phase, a controlled amount of water vapor is also present. The controlled amount of water vapor may be provided by placing a preselected amount of magnesium sulfate heptahydrate in the same chamber or enclosure with the object having the surface to be modified. In other embodiments, a controlled amount of water may be introduced into the reaction chamber or enclosure via an external water vapor feed. The reaction may take place under reduced pressure, relative to atmospheric pressure. In some embodiments, the reduced pressure may be 100 Torr or less. In other embodiments, the reduced pressure may be less than 10 Torr or less than 1 Torr.
The reaction may be conducted at a temperature in a range from about 150° C. to about 200° C. In various embodiments, the reaction may be conducted at a temperature of about 150° C., 155° C., 160° C., 165° C., 170° C., 175° C., 180° C., 185° C., or about 190° C. The reaction may be permitted to continue for about 2h, 6h, 8h, 18h, 24h, 48h, 72 h, 84h, or more.
In some embodiments, the covalently modified surface may have a structure of Formula II:
wherein R, M, n, h, j, k, m and V are as described above, in any combination. In some embodiments of the method, the covalently modified surface may have a formula of Formula 210, 211, 212, or 213 as described above, having any combination of permissible elements for each formula.
In various embodiments of the method, the surface may include a nucleophilic moiety selected from the group consisting of hydroxide, amino and thiol. The surface may be a metal, metal oxide, glass, polymer, or any combination thereof. The metal surface may include silicon, silicon oxide, hafnium oxide, indium tantalum oxide, alumina, or any combination thereof.
In various embodiments of the method, wherein the step of forming covalently modified surface may be performed on a DEP substrate or a EW substrate. The step of forming the covalently modified surface may include forming the covalently modified surface on at least one surface of a microfluidic circuit element of a microfluidic device. The microfluidic circuit elements may include walls, flow regions, pens, and electrode activation substrates, including DEP or EW substrates. The surface within the microfluidic circuit which may be covalently modified, may be all or substantially all of the surfaces facing fluid bearing portions of a microfluidic device. For example, in microfluidic devices 200, 230 the inner surface of the top electrode 210, the upper surface of the electrode activation substrate 206, the surfaces of the microfluidic circuit material 116 (See
I. Immiscible Medium.
Movement of aqueous droplets upon the surface of the substrate may be performed within a water immiscible fluidic medium distributed regionally within one or more flow regions (which may include flow channels) and, if present, within chambers fluidically connected to the flow regions. The water immiscible fluidic medium may have a kinematic viscosity greater than that of a droplet of pure water. The water immiscible fluidic medium may have a kinematic viscosity in the range of about 1 Centistoke (cSt) to about 15 cSt, where 1 cSt is equal to 1 millipascal or to 1 centipoise (CPS). In some embodiments, the water immiscible fluidic medium may have a viscosity in the range of about 3 cSt to about 10 cSt or about 3cSt to about 8 cSt. The water immiscible fluidic medium may be nonflammable at temperatures of at least 100° C. The water immiscible fluidic medium may be non-toxic to living biological cells over the duration of time that biological cells are processed, cultured or stored within the aqueous droplet within the water immiscible fluidic medium.
The water immiscible fluidic medium may have low or very little solubility in water. The water immiscible fluidic medium may dissolve less than about 5%, 4%, 3%, 2%, 1% or less than 1% of its total volume of water, when contacted with a layer of water (e.g., partitioning with water). The water immiscible fluidic medium may not solubilize more than about 5%, about 10% about 15%, about 20%, about 25%, or about 30% of the volume of an aqueous droplet present within the water immiscible fluidic medium at a temperature in the range of about 25° C. to about 38° C. In some embodiments, the water immiscible fluidic medium solubilizes less than about 20% of the volume of an aqueous droplet present within the water immiscible fluidic medium.
The water immiscible fluidic medium may include at least one organic or organosilicon compound having a backbone structure comprising atoms selected from carbon, silicon, and oxygen. In some embodiments, the water immiscible fluidic medium may include more than one organic/organosilicon compound, wherein the more than one compound is a polymeric organic/organosilicon compound having a range of molecular weights of the subunits of the polymeric compound. For example, the polymeric organic/organosilicon compound may have two different sub-units making up the polymer (e.g., a copolymer) and each of the two different sub-units may be present in a range of repeats, having a generic formula AaBb where A and B are two different polymer subunits, and a and b are the number of repeats of each subunit. The number of repeats, a and b, may not be a single integer but may be a range of repeat units.
In other embodiments, the water immiscible fluidic medium including more than one organic/organosilicon compound, may include a mixture of organic compounds, a mixture of organosilicon compounds, or any combination thereof. The water immiscible fluidic medium may include any suitable mixture of compounds having different chemical structures and/or molecular weights that will provide suitable performance.
A compound of the water immiscible fluidic medium may have a molecular weight of less than about 1000 Da, about 700 Da, about 500 Da, or about 350 Da. In other embodiments, the compound(s) of the water immiscible medium may have a higher molecular weight than about 1000Da and still provide suitable performance.
In various embodiments, the organic/organo silicon compound(s) of the water immiscible fluidic medium may have a backbone structure where the atoms making up the backbone are carbon, silicon or oxygen. The substituents of the backbone carbons may be hydrogen or fluorine. In some embodiments, the water immiscible fluidic medium may include one or more organo silicon compounds, where the backbone of the organosilicon compound(s) may include silicon and oxygen atoms. The silicon atoms of the organosilicon compound(s) may have carbon substituents, which in turn may have hydrogen or fluorine sub stituents. In some embodiments, the carbon substituents of an organosilicon compound may be all fluorine (e.g., perfluorinated). In other embodiments, the carbon substituents of an organosilicon compound may be partially fluorinated. In various embodiments, the substituents of carbon atoms of an organosilicon compound may be no more than about 90% fluorine, 80% fluorine, 70% fluorine, 60% fluorine, 50% fluorine, 40% fluorine, 30% fluorine, 20% fluorine or less.
In other embodiments, the organic compound(s) of the water immiscible fluidic medium may have a backbone structure where the atoms making up the backbone are carbon or oxygen. In some embodiments, the substituents of the backbone carbons may be hydrogen or fluorine. In other embodiments, the substituents of the backbone carbons may include an oxygen containing moiety such as an ether, carbonyl, or carbonate component. In some embodiments, the organic compound(s) of the water immiscible fluidic medium may have an all-carbon backbone structure. In some embodiments of the all-carbon backbone structure of the organic compound(s) of the water immiscible fluidic medium may have all fluorine substituents on the carbon atoms (e.g., is perfluorinated). In other embodiments, the substituents of an organic compound may be partially fluorinated (e.g., is not perfluorinated). In various embodiments, the substituents of carbon atoms of an organic compound, including a compound having an all-carbon backbone, may be no more than about 90% fluorine, 80% fluorine, 70% fluorine, 60% fluorine, 50% fluorine, 40% fluorine or less. In some embodiments, a suitable organic compound of the water immiscible fluidic medium may include or may be a monofluoro-substituted hydrocarbon such as 1-fluorooctane, 1-fluorodecane, 1-fluorododecane, or 1-fluorotetradecane.
In other embodiments, the organic compound(s) of the water immiscible fluidic medium may have no fluorine substituents on the carbons, but may have hydrogen substituents. In some embodiments, the organic compound(s) of the water immiscible fluidic medium may have unsaturated carbon-carbon linkages, e.g., an olefinic group either within the backbone carbons or at a terminal position.
In some embodiments, selection of an appropriate compound to be included in the water immiscible fluidic medium will include consideration of other properties of the compound. In various embodiments, a compound suitable for use within a water immiscible fluidic medium will not autofluoresce when illuminated by a laser, structured light projected into a microfluidic device, or daylight/laboratory lighting.
In other embodiments, the nature of the covalently modified hydrophobic surface will influence the selection of suitable compounds for use within the water immiscible fluidic medium. For example, a covalently modified surface may be sufficiently hydrophobic such that a droplet of water within a perfluorinated water immiscible fluidic medium may demonstrate sufficiently high surface tension that the droplet of water may not be movable using an opto-electrowetting configuration as described herein.
In some other embodiments, the nature of the microfluidic circuit material may influence selection of suitable compounds for use within the water immiscible fluidic medium. Swelling of the circuit material by the water immiscible fluidic medium may be kept within acceptable limits. For example, in some embodiments, if the microfluidic circuit material includes SU8 or a photopatternable aryl-substituted organosilicone, then linear hydrocarbon, linear fluorocarbon, or carbon-backbone compounds including cyclic, aryl or heteroaryl groups may be selected for use.
In other embodiments, the microfluidic circuit material may include other materials such as a photopatternable organosilicone containing no aryl substitution, and swelling may be limited to acceptable limits by use of different compounds in the water immiscible fluidic medium. For example, swelling of less than about 40%, 30%, 20%, or 10% compared to pre-exposure to the water immiscible fluidic medium may be acceptable. However, in some embodiments, a compound within the water immiscible fluidic medium that causes swelling may still be selected for use.
In some embodiments, the compound of the water immiscible fluidic medium may be an organic compound having a backbone containing carbon or oxygen atoms. In some embodiments, the organic compound may have a backbone that contains carbon atoms and does not contain oxygen atoms, and further where the carbon atom backbone is branched. In various embodiments, the branched carbon atom backbone of the organic compound of the water immiscible fluidic medium is acyclic. The organic compound of the water immiscible fluidic medium having a branched carbon backbone may further not contain any cyclized moiety.
While the above selection criteria may be used to select one or more compounds to be incorporated within a water immiscible fluidic medium, and eliminate compounds which may not provide acceptable performance, an acceptable water immiscible fluidic medium may be a multi-component mixture, and may include some portion of an individual organic or organosilicon compound that would not provide acceptable performance when used as a sole component of a water immiscible fluidic medium. For example, a component may be too highly fluorinated or may unacceptably swell the micro fluidic circuit material when used alone, but may be used in combination with other organic or organosilicon compounds to form a water immiscible fluidic medium.
Some suitable organic compounds for use in the water immiscible fluidic medium, either singly or in combination of any kind may include isocetane, 2-(Trifluoromethyl)-3-ethoxydodecafluorohexane (HFE-7500, 3M™, Novec™), heptamethyl nonane (HMN), bis(2-ethylhexyl) carbonate(TEGOSOFT® DEC, (Evonik)), and (Tridecafluoro-1, 1, 2, 2,-tetrahydrooctyl) tetramethydisiloxane (Gelest, Cat # SIB1816.0), or silicone oil (5 centistoke viscosity, Gelest Cat. # DMS-T05).
In some embodiments, the nature of the covalently modified hydrophobic surface will influence the selection of suitable compounds for use within the water immiscible fluidic medium. For example, a covalently modified surface may be sufficiently hydrophobic such that a droplet of water within a perfluorinated water immiscible fluidic medium may demonstrate sufficiently high surface tension that the droplet of water may not be movable using an opto-electrowetting configuration as described herein.
For example, with any of the hydrophobic layers comprising an unbranched alkane group of 10 or more carbons described herein (e.g., —(CH2)2—CH3, where n=9 or 11 or 15 or greater), the water immiscible fluidic medium may comprise an organic liquid having a branched carbon and having molecular weight of about 100 to 500 daltons, or about 100 to 400 daltons, or about 100 to 300 daltons, or about 150 to 500 daltons, or about 150 to 400 daltons, or about 150 to 300 daltons. The organic liquid can be partially fluorinated or unfluorinated. In some embodiments, the organic liquid is acyclic (does not comprise a ring in its structure). In some embodiments, the water immiscible fluidic medium consists essentially of or consists of the organic liquid. In some embodiments, the organic liquid is a carbonate or a hydrocarbon. In some embodiments, the organic liquid is bis(2-ethylhexyl) carbonate (e.g., Tegosoft DEC) or heptamethylnonane (HMN). Alternatively, mineral oil can be used.
In another example, with any of the hydrophobic layers comprising a short unbranched alkane and a perfluoroalkane group described herein (e.g., —(CH2)n—(CF2)m—CF3, wherein n=2 or greater and m=11 or greater), the water immiscible fluidic medium may comprise mineral oil or a linear alkane organic liquid of the formula CxH(2x+2), wherein x is from 9 to 16. In some embodiments, for the linear alkane organic liquid, x is 10, 11, 12, 13, or 14. In some embodiments, the linear alkane organic liquid is dodecane. In some embodiments, the water immiscible fluidic medium consists essentially of or consists of the linear alkane organic liquid.
J. Aqueous Droplet.
The aqueous droplet may contain one or more micro-objects, which may include a biological cell or a bead. The aqueous droplet may contain biological products which may include nucleic acid or protein. In some other embodiments, the aqueous droplet may contain reagents for an assay, which may be any kind of reagent such as an enzyme, an antibody, a fluorescently labeled probe, or a chemical reagent.
1. Surfactant.
In some embodiments, the aqueous droplet may also include a surfactant. The surfactant may increase the portability of the aqueous droplet within the water immiscible fluidic medium. In some embodiments, a suitable surfactant may include a non-ionic surfactant. In various embodiments, a surfactant may be, but is not limited to a polyethylene oxide-polypropylene oxide (PEO-PPO) block copolymer, e.g., a poloxamer such as a Pluronic® block alkylene oxide copolymer, including any of Pluronics F68 (ThermoFisher Cat. # 2400032), L31, or F127; a fatty ester ethoxylated sorbitan such as TWEEN® 20 (polysorbate 20) (Signa Aldrich Cat. # P1379) or TWEEN® 60 (polysorbate 60) (Sigma Aldrich P1629); 2, 4, 7, 9, Tetramethyl-5-decyne-4,7,-diol ethoxylate (TET, Sigma Aldrich Cat #9014-85-1); an ethoxylated nonionic fluorosurfactant such as Capstone® FS-30 (DuPont™, Synquest Laboratories Cat. # 2108-3-38); or N-(1,3-bis(Glucopyranoside)propan-2-yl)-3-Butyl-3-Cyclohexylheptanamide (Cy-Tripglu). In some embodiments, sodium dodecyl sulfate (SDS) may be used as a surfactant. In various embodiments, phosphate buffered saline (PBS) may be used as a surfactant. The surfactant may be added to the aqueous droplet in a range of about 1%, 3%, 5%, 10%, 15%, 20%, about 25% v/v or any value in between. In some embodiments, the surfactant is present (e.g., in a droplet) at a concentration less than or equal to 0.5% v/v, e.g., at a concentration ranging from 0.1% to 0.5%, 0.1% to 0.15%, 0.15% to 0.25%, 0.25% to 0.35%, or 0.35% to 0.5%, or any range defined by two of the foregoing endpoints. In some embodiments, the surfactant is present at about 0.2% v/v. It has been found that surfactant concentrations in such ranges below 0.5% v/v can be effective in preventing undesired adhesion or adsorption of cells and biological molecules to surfaces in the microfluidic device (which can interfere with droplet operations, such as moving the droplet via electrowetting and/or merging one droplet with another) while also avoiding fouling of such surfaces, which may occur at higher concentrations. Additionally, surfactants can also provide beneficial effects with respect to aspects of library preparation and/or amplification methods disclosed herein, as discussed in more detail below.
In some embodiments, the nature of the covalently modified hydrophobic surface will influence the selection of suitable surfactants included in the droplet. Selection of the surfactant(s) can be further influenced by the reagents and procedures being used. Appropriate selection of surfactants can be especially important when relatively high temperatures are used, as the high temperature may render some surfactants less effective in some contexts. Accordingly, the following guidance is provided. For each surfactant mentioned in the following discussion, in some embodiments, the surfactant is present in a droplet (e.g., in a droplet on which a given step is being performed, such as a combined droplet produced by merging a droplet comprising the surfactant and one or more reagents relevant to the step being performed) with a droplet comprising cells and/or nucleic acid) at a concentration less than or equal to 0.5% v/v, e.g., at a concentration ranging from 0.1% to 0.5%, 0.1% to 0.15%, 0.15% to 0.25%, 0.25% to 0.35%, or 0.35% to 0.5%, or any range defined by two of the foregoing endpoints. In some embodiments, the surfactant is present in a droplet at about 0.2% v/v.
For droplets containing cells on surfaces comprising hydrophobic layers comprising an unbranched alkane group of 10 or more carbons described herein (e.g., —(CH2)n—CH3, where n=15 or greater), movement of the droplet was found to be facilitated well by TET surfactant. The Cy-Tripglu and PEO-PPO block copolymers (e.g., Pluronics F68, L31, and F127) were also useful in this regard. These same surfactants can also be used in combination with DNA fragmentation reagents/in DNA fragmentation steps.
For droplets containing cells on surfaces comprising hydrophobic layers comprising a short unbranched alkane and a perfluoroalkane group described herein (e.g., —(CH2)n—(CF2)m—CF3, wherein n=2 or greater and m=11 or greater), movement of the droplet was found to be facilitated well by PEO-PPO block copolymers (e.g., Pluronics F68, L31, and F127). TET surfactant was also useful in this regard. These same surfactants can also be used in combination with DNA fragmentation reagents/in DNA fragmentation steps.
For enzymatic lysis of cells using proteinase K or equivalents thereof, surfactants are considered helpful in promoting complete lysis. It was also observed that the presence of a surfactant could improve movement of the droplet via electrowetting and improve the consistency of subsequent nucleic acid fragmentation reactions, where applicable. Non-ionic surfactants, including those with a large polar head group, can be useful for these purposes. A large polar head group can have a size greater than 750 daltons, such as greater than 800, 900, 1000, 1100, 1200, or 1300. In some embodiments, the polar head group is of a size ranging from 750 to 2000 daltons, such as from 750 to 1000, 1000 to 1200, 1200 to 1400, 1400 to 1600, 1600 to 1800, or 1800 to 2000 daltons In some embodiments, the surfactant used in combination with a lysis reagent such as a protease (e.g., proteinase K) is a polysorbate surfactant having a molecular weight of at least 1000 daltons (e.g., polysorbate 20). In some embodiments, the surfactant is octylphenol ethoxylate in which the ethoxylate group has an average length of at least 9 ethyloxide units, or at least 15, 20, 25, 30 or more ethyloxide units, e.g., Triton X-305. In some embodiments, the surfactant is Triton X-100 or Nonidet P-40 (NP-40).
In an A-tailing step (e.g., to prepare DNA for ligation, e.g., to attach adapter or barcode sequences), Cy-Tripglu was useful when the hydrophobic layer comprises an unbranched alkane group of 10 or more carbons described herein (e.g., —(CH2)n—CH3, where n=15 or greater). When the hydrophobic layer comprises a short unbranched alkane and a perfluoroalkane group described herein (e.g., —(CH2)n—(CF2)m—CF3, wherein n=2 or greater and m=11 or greater), the surfactant(s) already present from previous steps such as cell movement and lysis (see above) was sufficient, although additional surfactant such as described with respect to cell movement for such surfaces could be included (e.g., to maintain a total surfactant concentration within the 0.1% to 0.5% v/v range) without any significant adverse impact.
For droplets comprising a polymerase and/or in which amplification (e.g., PCR) is performed, the surfactant can be a polysorbate surfactant having a molecular weight of at least 1000 daltons (e.g., polysorbate 20). Polysorbate 20 was effective on either of hydrophobic layers comprising an unbranched alkane group of 10 or more carbons described herein (e.g., —(CH2)n—CH3, where n=15 or greater) or a short unbranched alkane and a perfluoroalkane group described herein (e.g., —(CH2)n—(CF2)m—CF3, wherein n=2 or greater and m=11 or greater). PEO-PPO block copolymers (e.g., Pluronics F68, L31, and F127) or TET surfactant could also be used. In some embodiments, a droplet comprising a nucleic acid comprises one or more of (i) a polysorbate (e.g., polysorbate 20) and (ii) TET, Cy-Tripglu, or a PEO-PPO block copolymer (e.g., Pluronics F68, L31, and F127); and a droplet comprising a nucleic acid polymerase comprises a polysorbate (e.g., polysorbate 20). Thus, upon merging such droplets, as in certain methods comprising amplification according to this disclosure, the combined droplet comprises a polysorbate (e.g., polysorbate 20) and optionally one or more of TET, Cy-Tripglu, or a PEO-PPO block copolymer (e.g., Pluronics F68, L31, and F127). The surfactant(s) in the droplet comprising a nucleic acid can be selected based on the guidance provided above.
K. Kits
The disclosure also provides kits that are suitable for transporting micro-objects, biological products, and/or reagents that are compatible with and/or soluble in aqueous media. The kits can comprise any of the microfluidic devices disclosed herein (e.g., microfluidic devices having an enclosure comprising a base and a microfluidic circuit structure, wherein the base comprises a hydrophobic monolayer covalently bonded to at least a portion of an upper surface of the base). The kits can further comprise a fluidic medium that is immiscible with aqueous media, other useful reagents (e.g., surfactants and the like), or any combination thereof.
L. Methods of Manufacturing Microfluidic Devices.
A microfluidic device of the disclosure, such as apparatus 400, can be manufactured by (i) bonding a spacing element 108 to an inner surface 428 of a cover 110 having at least one electrode configured to be connected to an AC voltage source (not shown), (ii) bonding the spacing element 108 (and associated cover 110) to a dielectric surface 414 of a substrate 104 having at least one electrode 418 configured to be connected to an AC voltage source (not shown), whereby the spacing element 108 becomes sandwiched between the inner surface 428 of the cover 110 and the dielectric surface 414 of the substrate 104, with the cover 110 and the substrate 104 oriented substantially parallel to one another, and the substrate 104, spacing element 108, and cover 110 collectively defining an enclosure 435 configured to hold a liquid, and (iii) forming, by vapor deposition, an outer hydrophobic layer 412 on at least a portion of the inner surface 428 of the cover 110 and an out hydrophobic layer 412 on at least a portion of the inner dielectric layer 414 of the substrate 104.
Through vapor deposition of amphiphilic molecules, the hydrophobic layers 422 and 412 can achieve densely packed monolayers in which the amphiphilic molecules are covalently bonded to the molecules of the inner surface 428 of the cover 110 and the inner dielectric surface 414 of the substrate 104, respectively. Any of the self-associating molecules described herein, and equivalents thereof, can be vapor deposited on the inner surfaces of a microfluidic apparatus. To achieve a desirable packing density, self-associating molecules comprising, for example, alkyl-terminated siloxane can be vapor deposited at a temperature of at least 110° C. (e.g., at least 120, 130, 140, 150, 160, etc.), for a period of at least 15 hours (e.g., at least 20, 25, 30, 35, 40, 45, or more hours). Such vapor deposition is typically performed under vacuum and in the presence of a water source, such as magnesium sulfate heptahydrate (i.e., MgSO4.7H20). Typically, increasing the temperature and duration of the vapor deposition produces improved characteristics of the hydrophobic layers 422 and 412. The vapor deposition process can be ootionally improved, for example, by pre-cleaning the cover 110 (with spacing elements 108) and substrate 104. For example, such pre-cleaning can include a solvent bath, such as an acetone bath, an ethanol bath, or a combination thereof. The solvent bath can include sonication. Alternatively, or in addition, such pre-cleaning can include treating the cover 110 (with spacing elements 108) and substrate 104 in an oxygen plasma cleaner. The oxygen plasma cleaner can be operated, for example, under vacuum conditions, at 100W for 60 seconds.
In some embodiments, the microfluidic device can further include a droplet generator. The droplet generator can be configured to selectively provide droplets of one or more liquid media (e.g., aqueous liquid media) into the enclosure or a microfluidic channel within the enclosure. The droplets can contain, for example, micro-objects, such as biological micro-objects (e.g., cells) or beads. Alternatively, or in addition, the droplets can contain reagents, such as lysis buffer, affinity reagents, detectable labels, enzymatic mixtures, etc.
Microfluidic channel 812 of apparatus 800 is connected to a subset of chambers 816, and thus is indirectly connected to microfluidic channel 814 via such chambers 816. As illustrated, microfluidic channel 812 and the chambers 816 connected thereto contains a fluidic medium 822 which is immiscible in the first fluidic medium 824. Thus, for example, fluidic medium 822 can be an aqueous medium, such as a cell culture medium. When fluidic medium 822 is a cell culture medium, the chambers 816 that contain culture medium can be used as culture chambers for growing cells, and microfluidic channel 812 can be a perfusion channel that provides a flow of fresh culture medium. As discussed herein, the flow of fresh culture medium in a perfusion channel can, via diffusion of molecules between the perfusion channel and a culture chamber, provide nutrients to the chamber and remove waste from the chamber, thus facilitating continued cell growth.
Another example a microfluidic apparatus comprises an enclosure having microfluidic channels 812, 814, a first plurality of chambers 916, and a second plurality of chambers 816, and a droplet generator 806 for providing fluidic droplets 820 to the enclosure. This embodiment presents a variation on the microfluidic apparatus 900 shown in
The microfluidic circuits formed by the microfluidic channels 812,814 and chambers 816, 916 are merely examples, and many other configurations of channels and chambers are encompassed by the disclosure. For example, in each of apparatuses 800and 900, microfluidic channel 812 and the chambers 816 directly connected to channel 812 are optional features. Thus, apparatuses 800 and 900 can lack perfusion channels and culture chambers.
In embodiments where microfluidic channel 812 is present, the substrate which helps to define channel 812 and/or directly connected chambers 816 (e.g., by forming the base of the channel and/or chambers) can have an electrowetting configuration. Alternatively, however, the substrate which helps to define the channel 812 and/or directly connected chambers 816 can lack an electrowetting configuration (e.g., and instead can have a DEP configuration, or neither an electrowetting nor a DEP configuration). In embodiments in which microfluidic channel 812 is present, and the substrate which helps to define channel 812 and/or directly connected chambers 816 has an electrowetting configuration, the outer hydrophobic surface of the substrate can be patterned to be more hydrophilic than the outer hydrophobic surface of the substrate which helps to define channel 814. The increased hydrophilicity can be achieved, for example, as discussed above.
The droplet generator 806 and any microfluidic circuit to which it provides droplets can be part of a microfluidic device (either an integral part or connected thereto), which can be like any of the microfluidic devices illustrated in the drawings or described herein. Although one droplet generator 806 is shown in
The droplet generator 806 itself can include an electrowetting configuration, and can thus comprise a substrate having a photoresponsive layer, as generally described in PCT Application No. PCT/US2016/069579, filed on Dec. 30, 2016. The photoresponsive layer which can comprise a-Si:H (e.g., as illustrated in U.S. Pat. No. 6,958,132), a photo-actuated circuit substrate (e.g., as illustrated in U.S. Patent Application Publication No. 2014/0124370), a phototransistor-based substrate (e.g., as illustrated in U.S. Pat. No. 7,956,339), or an electrically-actuated circuit substrate (e.g., as illustrated in U.S. Patent No. 8,685,344). Alternatively, the droplet generator can have a T- or Y-shaped hydrodynamic structure (e.g., as illustrated in U.S. Patents & Patent Application Publication Nos. 7,708,949, 7,041,481 (reissued as RE41,780), 2008/0014589, 2008/0003142, 2010/0137163, and 2010/0172803). All of the foregoing U.S. patent documents are incorporated by reference herein in their entirety.
As shown, the droplet generator 806 can comprise one or more fluidic inputs 802 and 804 (two are shown but there can be fewer or more) and a fluidic output 208, which can be connected to the microfluidic channel 814. Liquid media 822, 824, biological micro-objects 830, reagents, and/or other biological media can be loaded through the inputs 802 and 804 into the droplet generator 806. The droplet generator 806 can generate and output into the channel 814 droplets 820 of the liquid medium 822 (which can, but need not, contain one or more biological micro-objects 830), reagents, or other biological medium. If the channel 814 has an electrowetting configuration, the droplets 820 can be moved in the channel 814 utilizing electrowetting (or optoelectrowetting). Alternatively, the droplets 820 can be moved in the channel 814 by other means. For example, the droplets 820 can be moved in the channel 814 using fluidic flow, gravity, or the like.
As discussed above, the microfluidic channel 814 and select chambers 816/916 can be filled with a first fluidic medium 824, and microfluidic channel 812 and chambers 816 connected directly thereto can be filled with a second fluidic medium 822. The second fluidic medium 822 (hereinafter an “aqueous medium”) can be an aqueous medium, such as a sample medium for maintaining, culturing, or the like biological micro-objects 830. The first fluidic medium 824 (hereinafter an “immiscible medium”) can be a medium in which the aqueous medium 822 is immiscible. Examples of the aqueous medium 822 and the immiscible medium 824 include any of the examples discussed above for various media.
The droplet generator 806 can be utilized to load biological micro-objects and/or facilitate the running of biochemical and/or molecular biological workflows on the microfluidic apparatus.
At step 1002 of the process 100, a biological micro-object can be cultured in a holding pen filled with a sample medium (e.g., cell culture medium). For example, a micro-object 830 of
At step 1004, the cultured biological micro-object can be moved from the sample-medium-filled chamber 816 in which it was cultured to a chamber 816/916 filled with a medium in which the sample medium is immiscible. For example, the cultured micro-object 830 can be moved in a droplet 820 or 832 of sample medium 822 from one of the holding pens 816 into one of the holding pens 816/916, as illustrated in
At step 1006, the cultured biological micro-object can be subjected to one or more treatments or processes in the immiscible-medium-filled holding pen. For example, one or more droplets 820 containing one or more reagents can be produced by the droplet generator 806 and moved into an immiscible-medium-filled chamber 816/916 and merged with the droplet 832 containing the cultured biological micro-object 830, as shown in
In addition or as another example, one or more droplets containing one or more labeled capture micro-objects (not shown) having an affinity for a secretion or other material or materials of interest (e.g., nucleic acids such as DNA or RNA, proteins, metabolites, or other biological molecules) produced the cultured biological micro-object 830 can be generated by the droplet generator 806 and moved into the immiscible-medium-filled pen 816 or 916 and merged with the droplet of sample medium 822 containing the cultured biological micro-object 830 in a similar manner. In cases where the cultured biological micro-object 830 has already been lysed, capture micro-object-containing droplet 820 could contain one or more affinity beads (e.g., having affinity for nucleic acids, such as DNA, RNA, microRNAs, or the like) which, upon merger with the cell lysate-containing droplet in holding pen 816 or 916, could bind to target molecules present in the lysate.
At step 1008, the treated biological micro-object can be optionally processed. For example, if at step 1006, a capture object (not shown) is moved into the immiscible-medium-filled chamber 816/916 with the cultured biological micro-object 830, the chamber 816/916 can be monitored at step 1008 for a reaction (e.g., a fluorescent signal) indicative of a quantity of the material of interest bound to the labeled capture micro-object. Alternatively, such a capture micro-object (not shown) can be removed (e.g., in a droplet 822) from the chamber 816/916 and exported from the microfluidic device (not shown in
A substrate for a microfluidic device that includes both an electrowetting configuration and a dielectrophoresis (DEP) configuration may be formed as described in PCT/US2016/059234, filed Oct. 27, 2016, published as WO2017/075295, all of the content of which is incorporated by reference for all purposes.
Although specific embodiments and applications of the disclosure have been described in this specification, these embodiments and applications are exemplary only, and many variations are possible. For example, the methods of
A system for transporting micro-objects, biological products, and/or reagents that are compatible with and/or soluble in aqueous media is provided by the disclosure. The system can include, for example, any of the microfluidic devices disclosed herein (e.g., a microfluidic device having an enclosure comprising a base and a microfluidic circuit structure, wherein the base comprises a hydrophobic monolayer covalently bonded to at least a portion of an upper surface of the base). In addition, the system can include a fluidic medium and an aqueous droplet, wherein the fluidic medium and the aqueous droplet are immiscible fluids. The fluidic medium can be any of the immiscible media described herein, and the aqueous droplet can comprise any of the biological materials and/or chemical agents described herein (e.g., proteins, nucleic acids, detergents, surfactants, and the like).
As illustrated in
Typically, the electrical signal generation subsystem 304 will include a waveform generator (not shown). The electrical signal generation subsystem 304 can further include an oscilloscope (not shown) and/or a waveform amplification circuit (not shown) configured to amplify a waveform received from the waveform generator. The oscilloscope, if present, can be configured to measure the waveform supplied to the microfluidic device 320 held by the socket 302. In certain embodiments, the oscilloscope measures the waveform at a location proximal to the microfluidic device 320 (and distal to the waveform generator), thus ensuring greater accuracy in measuring the waveform actually applied to the device. Data obtained from the oscilloscope measurement can be, for example, provided as feedback to the waveform generator, and the waveform generator can be configured to adjust its output based on such feedback. An example of a suitable combined waveform generator and oscilloscope is the Red Pitaya™.
In certain embodiments, the nest 300 further comprises a controller 308, such as a microprocessor used to sense and/or control the electrical signal generation subsystem 304. Examples of suitable microprocessors include the Arduino™ microprocessors, such as the Arduino Nano™. The controller 308 may be used to perform functions and analysis or may communicate with an external master controller 154 (shown in
In some embodiments, the nest 300 can comprise an electrical signal generation subsystem 304 comprising a Red Pitaya™ waveform generator/oscilloscope unit (“Red Pitaya unit”) and a waveform amplification circuit that amplifies the waveform generated by the Red Pitaya unit and passes the amplified voltage to the microfluidic device 100. In some embodiments, the Red Pitaya unit is configured to measure the amplified voltage at the microfluidic device 320 and then adjust its own output voltage as needed such that the measured voltage at the microfluidic device 320 is the desired value. In some embodiments, the waveform amplification circuit can have a +6.5V to −6.5V power supply generated by a pair of DC-DC converters mounted on the PCBA 322, resulting in a signal of up to 13 V at the microfluidic device 100.
As illustrated in
In some embodiments, the nest 300 can include a thermal control subsystem 306 with a feedback circuit that is an analog voltage divider circuit (not shown) which includes a resistor (e.g., with resistance 1 kOhm+/-0.1%, temperature coefficient +/−0.02 ppm/CO) and a NTC thermistor (e.g., with nominal resistance 1 kOhm+/−0.01%). In some instances, the thermal control subsystem 306 measures the voltage from the feedback circuit and then uses the calculated temperature value as input to an on-board algorithm, such as a PID control loop algorithm. Output from the PID control loop algorithm can drive, for example, both a directional and a pulse-width-modulated signal pin on a Pololu™ motor drive (not shown) to actuate the thermoelectric power supply, thereby controlling the Peltier thermoelectric device.
In some embodiments, the thermal control subsystem configured to regulate a temperature of the microfluidic device comprises a thermal control circuit to adjust a temperature of the microfluidic device. The thermal control circuit can be configured to follow a three-phase temperature control procedure with rules correlating a temperature value measured by the thermistor with a target temperature and a power output of Peltier thermoelectric device, the rules comprising:
A Proportionate-Integral-Derivative (PID) control algorithm is a commonly-used control algorithm, used for closed-loop feedback that minimizes the error between the setpoint value of a given process variable and the current measured value of that variable. The PID control algorithm calculates a correction to system's output based on the value of the error, the integral of the error, and the derivative of the error. Output from the PID control loop algorithm can drive, for example, both a directional and a pulse-width-modulated signal pin on a Pololu™ motor drive (not shown) to actuate the thermoelectric power supply, thereby controlling the Peltier thermoelectric device.
In some embodiments, the first value is 70% to 100% power output of the Peltier thermoelectric device. In some embodiments, the first value is 100% power output. In some embodiments, the second value is a power output value determined from calibration data correlating a plurality of target temperature values correlated with a plurality of power output values.
In some embodiments, the target temperature values correlated to the power output values are determined by equilibrating a calibration chip comprising a thermocouple with the Peltier thermoelectric device at each of the power output values and associating the temperature registered by the thermocouple following equilibration with the power output value. In some embodiments, the plurality of target temperature values comprises at least 4, 5, 6, 7, 8, 9, or 10 values in the range of 0° C. to 100° C. In some embodiments, a power output value corresponding to a target temperature value between values represented in the calibration data is determined by linear interpolation. For example, the calibration data can comprise a series of power output values ranging from −100% (maximum cooling) to 100% (maximum heating) (e.g., at least 4, 5, 6, 7, 8, 9, or 10 values) and the associated equilibrium temperatures determined empirically for each of these values. The values can be, but are not necessarily, evenly distributed over the range of power outputs. From these data, appropriate power output values for any arbitrary temperature from the minimum to maximum observed temperatures can be determined by a suitable approach such as linear interpolation of the calibration data.
In some embodiments, separate sets of calibration data are provided for use in heating or cooling steps. The data for use in heating steps can be generated by first equilibrating at a −100% power output value and progressively increasing the power output to correspond to each power output value being included in the calibration data, equilibrating, and measuring the temperature. Similarly, the data for use in cooling steps can be generated by first equilibrating at a 100% power output value and progressively decreasing the power output to correspond to each power output value being included in the calibration data, equilibrating, and measuring the temperature.
The nest 300 can include a serial port 324 which allows the microprocessor of the controller 308 to communicate with an external master controller 154 via the interface 310 (not shown). In addition, the microprocessor of the controller 308 can communicate (e.g., via a Plink tool (not shown)) with the electrical signal generation subsystem 304 and thermal control subsystem 306. Thus, via the combination of the controller 308, the interface 310, and the serial port 324, the electrical signal generation subsystem 304 and the thermal control subsystem 306 can communicate with the external master controller 154. In this manner, the master controller 154 can, among other things, assist the electrical signal generation subsystem 304 by performing scaling calculations for output voltage adjustments. A Graphical User Interface (GUI) (not shown) provided via a display device 170 coupled to the external master controller 154, can be configured to plot temperature and waveform data obtained from the thermal control subsystem 306 and the electrical signal generation subsystem 304, respectively. Alternatively, or in addition, the GUI can allow for updates to the controller 308, the thermal control subsystem 306, and the electrical signal generation subsystem 304. In some embodiments, an external master controller comprises a graphical user interface configured to receive operator input and for processing and transmitting the operator input to the controller for controlling one or both of the electrical signal generation subsystem and the thermal control subsystem. In some embodiments, the controller is configured to transmit to the external master controller data and/or information sensed or received, or otherwise calculated based upon data or information sensed or received, from one or both of the electrical signal generation subsystem and the thermal control subsystem.
As discussed above, system 150 can include an imaging device 194. In some embodiments, the imaging device 194 comprises a light modulating subsystem 330 (See
In certain embodiments, the imaging device 194 further comprises a microscope 350. In such embodiments, the nest 300 and light modulating subsystem 330 can be individually configured to be mounted on the microscope 350. The microscope 350 can be, for example, a standard research-grade light microscope or fluorescence microscope. Thus, the nest 300 can be configured to be mounted on the stage 344of the microscope 350 and/or the light modulating subsystem 330 can be configured to mount on a port of microscope 350. In other embodiments, the nest 300 and the light modulating subsystem 330 described herein can be integral components of microscope 350.
In certain embodiments, the microscope 350 can further include one or more detectors 348. In some embodiments, the detector 348 is controlled by the imaging module 164. The detector 348 can include an eye piece, a charge-coupled device (CCD), a camera (e.g., a digital camera), or any combination thereof. If at least two detectors 348 are present, one detector can be, for example, a fast-frame-rate camera while the other detector can be a high sensitivity camera. Furthermore, the microscope 350 can include an optical train configured to receive reflected and/or emitted light from the micro fluidic device 320 and focus at least a portion of the reflected and/or emitted light on the one or more detectors 348. The optical train of the microscope can also include different tube lenses (not shown) for the different detectors, such that the final magnification on each detector can be different.
In certain embodiments, imaging device 194 is configured to use at least two light sources. For example, a first light source 332 can be used to produce structured light (e.g., via the light modulating subsystem 330) and a second light source 334 can be used to provide unstructured light. The first light source 332 can produce structured light for optically-actuated electrokinesis and/or fluorescent excitation, and the second light source 334 can be used to provide bright field illumination. In these embodiments, the motive module 164 can be used to control the first light source 332 and the imaging module 164 can be used to control the second light source 334. The optical train of the microscope 350 can be configured to (1) receive structured light from the light modulating subsystem 330 and focus the structured light on at least a first region in a microfluidic device, such as an optically-actuated electrokinetic device, when the device is being held by the nest 300, and (2) receive reflected and/or emitted light from the microfluidic device and focus at least a portion of such reflected and/or emitted light onto detector 348. The optical train can be further configured to receive unstructured light from a second light source and focus the unstructured light on at least a second region of the microfluidic device, when the device is held by the nest 300. In certain embodiments, the first and second regions of the microfluidic device can be overlapping regions. For example, the first region can be a subset of the second region.
In
In some embodiments, the second light source 334 emits blue light. With an appropriate dichroic filter 346, blue light reflected from the sample plane 342 is able to pass through dichroic filter 346 and reach the detector 348. In contrast, structured light coming from the light modulating subsystem 330 gets reflected from the sample plane 342, but does not pass through the dichroic filter 346. In this example, the dichroic filter 346 is filtering out visible light having a wavelength longer than 495 nm. Such filtering out of the light from the light modulating subsystem 330 would only be complete (as shown) if the light emitted from the light modulating subsystem did not include any wavelengths shorter than 495 nm. In practice, if the light coming from the light modulating subsystem 330 includes wavelengths shorter than 495 nm (e.g., blue wavelengths), then some of the light from the light modulating subsystem would pass through filter 346 to reach the detector 348. In such an embodiment, the filter 346 acts to change the balance between the amount of light that reaches the detector 348 from the first light source 332 and the second light source 334. This can be beneficial if the first light source 332 is significantly stronger than the second light source 334. In other embodiments, the second light source 334 can emit red light, and the dichroic filter 346 can filter out visible light other than red light (e.g., visible light having a wavelength shorter than 650 nm).
In some embodiments, methods disclosed herein comprise performing nucleic acid synthesis (e.g., reverse transcription or amplification, such as PCR, e.g., qPCR) in a droplet upon the droplet actuation surface of a microfluidic device. The microfluidic device can have any of the features described herein with respect to microfluidic devices. Exemplary embodiments of microfluidic devices, and methods of using same, are also provided in the Numbered Embodiments section below. The ability to generate precisely sized droplets within the system (as shown in
In some embodiments, methods disclosed herein comprise merging a (first) droplet comprising nucleic acid with a (second) droplet comprising a nucleic acid polymerase, and a buffer and precursors (e.g., nucleotides, primers, etc.) that support a polymerase activity of the nucleic acid polymerase and incubating the combined droplet upon the droplet actuation surface, under conditions that promote amplification of the nucleic acid. The second droplet can be merged with the first droplet by applying an electrowetting force to the second and/or the first droplet. In some embodiments, the nucleic acid polymerase is suitable for performing a reverse transcription reaction. Alternatively, the nucleic acid polymerase can be suitable for performing polymerase chain reaction (PCR) or for performing a whole genome amplification reaction. In some embodiments, the second droplet and/or the combined droplet comprises oligonucleotides (e.g., primers) suitable for initiating nucleic acid amplification. The oligonucleotides can include a nucleic acid-based bar code and/or a poly-dT sequence. At least some of the oligonucleotides can be linked to one or more capture beads.
In some embodiments, incubating the combined droplet under conditions that promote amplification comprises adjusting the temperature of the microfluidic device to a first temperature that is sufficient to cause the nucleic acid originating from the first droplet to denature (partially or fully). The first temperature can be at least about 85° C. (e.g., at least about 88° C., about 90° C., about 92° C., about 93° C., about 94° C., about 95° C., or greater).
In some embodiments, incubating the combined droplet under conditions that promote amplification comprises adjusting the temperature of the microfluidic device to a second temperature that promotes priming of the nucleic acid originating from the first droplet and/or the template-based extension of the primed nucleic acid. The second temperature can be about 35° C. to about 75° C. or 40° C. to about 75° C. (e.g., about 50° C. to about 70° C., or about 55° C. to about 65° C.). In some embodiments, such as embodiments involving whole genome amplification, the second temperature can be about 35° C. to about 60° C. (e.g., about 35° C. to about 45° C., or about 45° C. to about 55° C.). In some embodiments, such as embodiments involving PCR, the second temperature can be about 45° C. to about 75° C. (e.g., about 45° C. to about 55° C., about 50° C. to about 60° C., about 55° C. to about 65° C., about 60° C. to about 70° C., or about 65° C. to about 75° C.).
In some embodiments, incubating the combined droplet under conditions that promote amplification comprises: adjusting the temperature of the microfluidic device to a second temperature that promotes priming of the nucleic acid originating from the first droplet; and adjusting the temperature of the microfluidic device to a third temperature that promotes the template-based extension of the primed nucleic acid. The second temperature can be about 35° C. to about 67° C. or 50° C. to about 67° C. (e.g., about 55° C. to about 65° C., or about 58° C. to about 62° C.); and/or the third temperature can be about 50° C. to about 80° C. or 65° C. to about 80° C. (e.g., about 70° C. to about 78° C., or about 72° C. to about 76° C.). In some embodiments, such as embodiments involving whole genome amplification, the second temperature can be about 35° C. to about 60° C. (e.g., about 35° C. to about 45° C., or about 45° C. to about 55° C.). In some embodiments, such as embodiments involving PCR, the second temperature can be about 45° C. to about 67° C. (e.g., about 45° C. to about 55° C., about 50° C. to about 60° C., about 55° C. to about 65° C., or about 60° C. to about 67° C.). In some embodiments, such as embodiments involving whole genome amplification, the third temperature can be about 50° C. to about 75° C. (e.g., about 50° C. to about 60° C., or about 60° C. to about 75° C.). In some embodiments, such as embodiments involving PCR, the third temperature can be about 65° C. to about 80° C. (e.g., about 65° C. to about 75° C., about 67° C. to about 78° C., about 70° C. to about 80° C., or about 70° C. to about 74° C.).
In some embodiments, incubating the combined droplet under conditions that promote amplification comprises cycling the temperature of the microfluidic device between the first and second temperatures. In other embodiments, incubating the combined droplet under conditions that promote amplification comprises cycling the temperature of the microfluidic device between the first, second, and third temperatures. For example, at least 10 cycles can be performed (e.g., at least 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or more cycles are performed).
In some embodiments, a three-phase temperature control procedure is used to adjust the temperature of the microfluidic device using a Peltier thermoelectric device. The procedure can comprise setting the power output of the Peltier thermoelectric device to a first value if the difference between the target temperature and a measured temperature (e.g., by a thermistor associated with the microfluidic device) is larger than N; setting the power output to a second value lower than the first value if the difference between the target temperature and the thermistor-measured temperature is equal to or smaller than N and larger than M; and determining the power output by a proportionate-integral-derivative (PID) loop controller with the thermistor-measured temperature as an input if the difference between the target temperature and the thermistor-measured temperature is smaller than or equal to M, where M may be in the range of 7° C. to 13° C. and N may be in the range of 2° C. to 4° C. In some embodiments, M is 3° C. and N is 10° C. The procedure can have any of the additional features described with respect to the thermal control circuit configured to follow rules corresponding to such a procedure in the section concerning Systems.
In some embodiments, qPCR is performed. For example, a detection reagent can be provided together with the amplification reagents and signal from the detection reagent (e.g., fluorescence) indicative of the quantity of DNA present can be measured as the reaction proceeds. In some embodiments, the detection reagent is an intercalating dye.
In some embodiments, an amplification reaction other than PCR is performed. Based on the teachings provided herein, one skilled in the art can adapt procedures for any number of nucleic acid amplification approaches to be performed within a microfluidic device described herein. Exemplary additional amplification approaches include NASBA (nucleic acid sequence based amplification), SDA (strand displacement amplification), LAMP (loop-mediated isothermal amplification), RCA (rolling circle amplification), and TMA (transcription-mediated amplification. See, e.g., U.S. Pat. No. 5,705,365 (TMA); U.S. Pat. No. 6,326,173 and Journal of Virological Methods 151:283-293 (2008) (NASBA); U.S. Pat. No. 5,648,211 (SDA); U.S. Pat. No. 6,410,278 (LAMP); and U.S. Pat. No. 6,287,824 (RCA). One skilled in the art will understand what reagents are appropriate to provide. Each of these methods involves DNA synthesis, and as such involves the use of DNA Polymerases, nucleotides, and divalent cations (supplied as a salt), particularly magnesium, in a solution conducive to DNA polymerization and in which the template is present. The methods vary in terms of providing additional catalytic activities, the use of thermocycling or isothermal incubation, and the use and structure of primers.
A. Electrowetting Microfluidic Device Design Functional at a Broad Range of Temperatures
A microfluidic device having an electrowetting configuration may be provided for preparing sequencing libraries and/or amplifying nucleic acid, e.g., from a small number of selected cells (e.g., 10-100 cells) in a cost-efficient and high-throughput manner. Use of agents can be minimized and automatic workflow can be achieved by performing the workflow on the microfluidic device according to the present disclosure. In doing so, we have found it significant that the reagents located within aqueous droplet can be formulated so as not foul the surface of the microfluidic device having the electrowetting configuration. Guidance in this regard is provided in the discussion of surfactants above.
Further, the electrowetting device can be thermally cycled between low temperatures and high temperatures near the freezing and boiling points of water at sea level (for example, 4° C. to 98° C.) while avoiding breakdown of the hydrophobic layer, such as areas wherein fluid can directly contact the semi-conductive layer underneath the hydrophobic layer, resulting in an electrical short) and the resulting trapping (or “pinning”) of droplets to the breakdown points.
Features that can contribute to functionality of the microfluidic device and performance of the methods described herein while minimizing breakdown of the hydrophobic layer are described above and exemplified in the Examples and Numbered Embodiments below.
Any kind of DNA library preparation protocol may be adapted for use within the microfluidic device having an optoelectronic wetting configuration, and several different versions are described herein. Such DNA library preparation protocol includes commercially available KAPA Hyper Plus (Roche) and Nextera™ XT (Illumina).
A. Culturing Cells
In some embodiments, cells are cultured in the microfluidic device (
Cells of interest then can be selectively exported from their corresponding sequestration pens, optionally pooled, and transported to the EW section of the chip (or EW chip). The cells can be encapsulated in a droplet surrounded by a water immiscible medium (e.g., oil or organic liquid) at the DEP/EW interface. The cell selection can be based on rate of cell growth, morphology, assay results, or any comb thereof. As discussed above, the droplet comprising cells can further comprise a surfactant, which can aid in movement of the droplet.
B. Lysing Cells
In some embodiments, the method comprises lysing one or more cells in an EW section of a microfluidic device (or an EW microfluidic device) (
Examples of a suitable lysing agent include proteases such as proteinase K, including a heat sensitive version of proteinase K, which is commercially available. Conditions for lysis can be varied depending on a concentration of the lysing agent and a ratio of the first droplet volume to the second droplet volume. For example, cells can be incubated with 1mg/mL proteinase K at 50° C. -65° C. for about 20-40 (e.g., about 30) minutes. The second droplet contains 2mg/mL proteinase K if a ratio of the first droplet volume to the second droplet volume is 1:1.
The lysing reagent is an agent that can be inactivated/neutralized. For example, proteinase K can be heat inactivated, e.g., at 85° C. -95° C. for about 15-25 (e.g., 20) minutes.
A surfactant in the first droplet can prevent cells from sticking to the microfluidic device's surfaces (surfactant selection can be influenced by the chemical structure of the hydrophobic layer of the device, as discussed in detail herein).
A surfactant in the second droplet (lysing reagent droplet) is used to prevent the reagents in the second droplet and the first combined droplet from sticking to (or “fouling”) the microfluidic device surfaces. For example, 0.1-0.5% (e.g., 0.2%) polysorbate having a molecular weight of at least 750 daltons, such as polysorbate 20 (Tween 20®), may be used to improve lysis performance and mobility of the first combined droplet (see, e.g., Example 3-B below). Any non-ionic detergent with a large polar group could be substituted (e.g., an oxtylphenol ethoxylate, optionally where the ethoxylate group has an average length of at least 9 ethyloxide units, or at least 15, 20, 25, 30 or more ethyloxide units, such as Triton X-305, Triton X-100, or the like, or a nonyl phenoxypolyethoxylethanol, optionally where the polyethylene glycol chain has a length of at least 9 ethyoxide units, or at least 15, 20, 25, 30 or more ethyloxide units, such as NP-40).
C. Fragmenting DNA
In some embodiments, the method further comprises fragmenting DNA (e.g., gDNA) released by cell lysis (
Then, the fragmentation reaction is stopped by, for example, raising the temperature to 65° C. (thereby denaturing fragmentase enzyme(s)). In some embodiments, the droplet containing the double-stranded DNA cutting reagent includes a surfactant. Appropriate surfactants are discussed above in the section concerning aqueous droplets.
D. Adding Adapters to DNA Fragments
The method may further comprise adding adapters to DNA fragments (
In a first step, 3′ A nucleotide overhangs are generated at the ends of the DNA fragments. The second combined droplet (from step 1130) is merged with a fourth droplet containing an A-tailing enzyme (e.g., a polymerase with A-tailing activity, such as Taq polymerase) and appropriate reagents to form a third combined droplet. In some embodiments, the fourth droplet comprises Taq polymerase and a mixture of dNTPs. The third combined droplet is incubated for an appropriate time and temperature, e.g., about 60° C. to about 70° C. (e.g., about 62° C. to about 68° C., or about 65° C.), for at least about 15 minutes (e.g., about 15 to 45 minutes, about 20 to about 40 minutes, about 25 to about 35 minutes, or about 30 minutes). For example, the third combined droplet is incubated at 65° C. for 30 minutes. Polymerases other than Taq polymerase can be used (e.g., as provided in the commercially available KAPA A-tailing mixture).
The second step is to ligate double-stranded adapters having a 5′ T nucleotide overhang at one or both ends. The third combined droplet (from step 1140A) is merged with a fifth droplet comprising a ligase, the double-stranded adapters, and appropriate reagents (e.g., ATP) to form a fourth combined droplet. In some embodiments, the ligase is T4 ligase. The fourth combined droplet is incubated for appropriate time and temperature, e.g., about 15° C. to about 25° C. (e.g., about 18° C. to about 22° C., or about 20° C.) for at least about 10 minutes (e.g., about 10 to about 20 minutes, about 12 to about 18 minutes, or about 15 minutes). Ligases other than T4 can be used. The ligase may be inactivated by adjusting the temperature of the microfluidic device to a temperature of about 80° C. to about 90° C. (e.g., about 82° C. to about 88° C., or about 85° C.), optionally for at least about 10 minutes (e.g., about 10 to about 20 minutes, about 12 to about 18 minutes, or about 15 minutes).
Each adapter can include a unique barcode, and/or a target sequence for amplification. Combinations of barcodes can be used with different samples so that each sample is uniquely labeled. An example of barcoding is described in Examples 2-C and 2-D below and also in
The droplet containing the polymerase/A-tailing mixture can include a surfactant. Appropriate surfactants are discussed above in the section concerning aqueous droplets. In some embodiments, the same type of surfactant used in moving cell-containing droplets in prior step 1110 is used.
E. Tagmentation (Alternative for Fragmentating and Adding Adapters)
Alternatively, fragmentation and adding adapters to DNA fragments (steps 1130 and 1140) can be combined into a tagmentation step, which is a process that fragments DNA and tags the DNA with adapter sequences in a single step (as depicted in
The reaction temperature and time may vary depending on the other conditions regarding the droplet. The incubation temperature and time may be about 50° C. to about 60° C. (e.g., about 52° C. to about 58° C., or about 55° C.), and at least about 3 minutes (e.g., about 3 to 7 minutes, about 4 to about 6 minutes, or about 5 minutes). For example, the second combined droplet may be incubated at 55° C. for 5 minutes.
In some embodiments, the method further comprises mixing the second combined droplet with a fourth droplet containing a tagmentation stop buffer to form a third combined droplet. The reaction may be neutralized shortly after the incubation using tagmentation stop buffer, for example, after 5 minutes of incubation. The tagmentation stop buffer denatures the transposase. For the stop buffer, 0.1%42% SDS, Nextera NT buffer or the like may be used.
Although Nextera tagmentation adapter sequences do not include barcodes, barcodes may be added if desired through an additional PCR amplification step. It is advisable to purify tagmented DNA in the third combined droplet before performing PCR amplification, as tagmentation stop buffer present in the droplet may otherwise interfere with PCR. In some embodiments, magnetic beads are used to purify DNA. Methods of purifying DNA on chip have been described, for example, in U.S. Patent Application Publication No. 2015/0038344, the entire contents of which are incorporated herein by reference.
F. DNA Fragment Amplification (
In some embodiments, DNA is amplified following adapter attachment. Amplification may be performed within the microfluidic device (
Amplification procedures are discussed in detail in the section above concerning nucleic acid synthesis. The fourth combined droplet containing DNA fragments from step 1140B, or if tagmentation is performed, the third combined droplet prior to amplification is purified. The purified DNA droplet (or the fourth combined droplet from step 1140B) is merged with a sixth droplet containing an amplification mixture to form a fifth combined droplet. Then, temperature cycling on the fifth combined droplet is performed. For the DNA amplification, a high-fidelity DNA polymerase (e.g., KAPA HiFi polymerase, or a thermostable DNA polymerase comprising 3′ to 5′ editing exonuclease activity or the like) can be used. The times for each cycle may vary, including the time for temperature increase/decrease. The standard temperature cycle may include 95° C. for 70 seconds, 55° C. for 30 second, 72° C. for 50 seconds. Depending on the desired amount of amplification, temperature cycling can be performed with at least 10, 20, or 30 cycles, or about 10 to 20 cycles, or about 12 to 15 cycles. In some embodiments, 4-15 cycles are performed. In some embodiments, 4-6 cycles or 10-14 cycles are performed. In some embodiments, 12 cycles are performed.
For DNA fragments from step 1140B, each primer may include a sequence complementary to an adapter target sequence and, optionally, a sequence that can be used for further amplification and/or sequencing (e.g., Nextera P5 and P7 sequences). For DNA fragments produced by tagmentation, each primer may include a barcode sequence located between the adapter target sequence and the sequence useful for further amplification and/or sequencing.
The amplification mix can include a surfactant, e.g., to prevent DNA and DNA polymerase from fouling surfaces. For example, 0.1%-0.5% (or 0.2%) Tween-20 is preferred. Alternatively, 0.1%-0.5% (or 0.2%) of a PEO-PPO block co-polymer can be used (e.g., Pluronic F68, Pluronic F127). Alternatively, 0.1%-0.5% (or 0.2%) of 2,4,7,9-tetramethyl-5-decyne-4,7-diol ethoxylate (TET) can be used. Additional relevant discussion of surfactants is provided within the section concerning aqueous droplets.
The amplification conditions can be applied to the amplification of any of the nucleic acids (or fragments thereof), such as the amplifications described in below-numbered embodiments 160-165 and 167-169.
G. Subsequent Steps
Amplified DNA fragments can be purified (
As an alternative to amplification within the microfluidic device, DNA fragments can be pooled and exported out of the chip (
H. cDNA Library Preparation
In some embodiments, a cDNA library is prepared. Following lysis as described above, the first combined droplet can be merged with a third droplet of aqueous medium to form a second combined droplet, wherein the third droplet comprises a reverse transcriptase and suitable reagents (e.g., dNTPs and oligo-dT for use as a primer). The second combined droplet can be incubated to permit reverse transcription, thereby forming cDNA. Incubating can comprise adjusting the temperature of the microfluidic device to a temperature of about 50° C. to about 60° C. (e.g., about 52° C. to about 58° C., or about 55° C.), for at least about 1 minute (e.g., about 1 to 5 minutes, about 1 to about 3 minutes, or about 2 minutes); and adjusting the temperature of the microfluidic device to a temperature of about 37° C. to about 45° C. (e.g., about 40° C. to about 43° C., or about 42° C.), for at least about 45 minutes (e.g., at least about 50, about 55, about 60 minutes, or more). The oligo-dT can further comprise a 5′ sequence useful as a primer binding site for downstream steps, or be linked to a bead, such as a magnetic bead. In further steps, droplets comprising cDNA can be amplified by merging with a droplet comprising an amplification mixture, e.g., including appropriate primers for the PCR stage of RT-PCR and otherwise essentially as described above. The same steps described above following amplification can be performed to complete preparation of a cDNA library.
The systems used in these examples included microfluidic devices (Berkeley Lights, Inc.) having at least 12 chambers fluidically connected to a flow path, and at least one inlet and one outlet for introduction and export of fluidic media, droplets containing cells, reagents and/or prepared samples according to the experiments. The chambers have a volume of about 80 nanoliters. The device has substrates configured to provide electrowetting, where at least the surfaces of the substrates included covalently modified surfaces. The covalently modified surfaces were selected from one of the two following modifications:
The aqueous immiscible medium used to fill the chambers and the flow path of the microfluidic device was selected from one of the following materials:
Surfactants may be added to the water-immiscible fluidic medium. In some embodiments, a suitable surfactant may be a non-ionic surfactant, such as sorbitane monooleate (Span 80, Aldrich Cat. # 1338-43-8).
The system also included an optical instrument manufactured by Berkeley Lights, Inc. to control the microfluidic device. The instrument included: a mounting stage for the device coupled to a temperature controller; a pump and fluid medium reservoir component; and an optical train including a camera and a structured light source suitable for activating the optoelectronic wetting substrates within the device. The instrument also included a movable magnet under the microfluidic device.
Cells. Cells used in all experiments were a B-lymphocyte cell line (Coriell Institute, Cat. # GM12878).
A microfluidic device (Berkeley Lights, Inc.) having a base that included an electrode activation substrate having a semiconductive layer of photosensitive silicon and a dielectric layer having an upper surface of alumina, a cover having a glass support with an ITO electrode, and microfluidic circuit material of photopatterned silicone separating the base and the cover, was treated in an oxygen plasma cleaner (Nordson Asymtek) for 1 min, using 100W power, 240 mTorr pressure and 440 sccm oxygen flow rate. The plasma-treated microfluidic device was treated in a vacuum reactor with trimethoxy (3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 10, 10, 11, 11, 12, 12, 13, 13, 14, 14, 15, 15, 16, 16, 16)-nonaicosafluorohexadecyl)silane (0.3g, details of synthesis as described in WO 2017/205830, published Nov. 30, 2017) in a foil boat in the bottom of the vacuum reactor in the presence of magnesium sulfate heptahydrate (0.5g, Acros), as a water reactant source, in a separate foil boat in the bottom of the vacuum reactor. The chamber was then pumped to 750 mTorr using a vacuum pump and sealed. The vacuum reactor was placed within an oven heated to 180° C. for 24-48 h. After cooling to room temperature and introducing argon to the evacuated chamber, the microfluidic device having an outer hydrophobic layer of dimethoxy (3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 10, 10, 11, 11, 12, 12, 13, 13, 14, 14, 15, 15, 16, 16, 16-nonacosafluoro-hexadecyl)siloxy moieties on all interior surfaces was removed from the reactor. Following removal, the microfluidic device was primed with silicone oil (5 centistoke viscosity, Gelest Cat. # DMS-T05) prior to use.
Culture Cells on Chip (
A microfluidic device (chip) including a first section that has an electrowetting (EW) configuration and a second section that includes a dielectrophoresis (DEP) configuration can be used to culture cells. Alternatively, two separate chips may be provided such that a DEP chip is connected to an EW chip (e.g., by an export/import tube). Cells are cultured in sequestration pens in the DEP section of the chip (or DEP chip), as described in e.g., WO 2016/141343. Cultured cells can be assayed in their sequestration pens to identify cells of interest, as described, e.g., in PCT/US2014/061837, published as WO 2015/061497; PCT/US2014/061848, published as WO 2015/061506; PCT/US2015/027795, published as WO 2017/181135, by epitope labeling (e.g., with fluorescently labeled antibodies), or any other microfluidic assay known in the art.
Cells of interest then can be selectively exported from their corresponding sequestration pens, optionally pooled, and transported to the EW section of the chip (or EW chip). The cells can be encapsulated in a droplet surrounded by a water immiscible medium or oil at the DEP/EW interface. Cell selection can be based on rate of cell growth, morphology, assay results, or any combination thereof.
Lyse Cells (
Cell lysis was performed in an electrowetting section of a chip (or an EW chip). A first droplet containing cells was merged with a second droplet containing a lysing reagent to form a first combined droplet. As an example, the first droplet can be 10 nL in volume and can contain 5-100 cells, 10-50 cells, or about 30 cells, and the second droplet can be 10 nL in volume; however, different droplet sizes, different numbers of cells, and different ratios of first droplet volume to second droplet volume can be used.
An appropriate surfactant in the first droplet can prevent cells from adhering to the microfluidic device's surfaces. See the guidance regarding surfactant selection provided herein.
Examples of a suitable lysing agent include a protease such as proteinase K and more heat sensitive versions of proteinase K, which are commercially available. Conditions for lysis can be varied depending on a concentration of the lysing agent and a ratio of the first droplet volume to the second droplet volume. For example, cells can be incubated with 1mg/mL proteinase K at 50° C. -65° C. for 30 minutes; to expose cells to this concentration of proteinase K, the second droplet can be provided with 2mg/mL proteinase K if the volume ratio of the first droplet to the second droplet is 1:1.
The lysing reagent can be an agent that can be inactivated/neutralized. For example, proteinase K can be heat inactivated, e.g., at 85° C. -95° C. for up to 20 minutes.
A surfactant in the second droplet (lysing reagent droplet) was used to prevent the reagents and/or cellular material in the second droplet and the first combined droplet from sticking (or “fouling”) to the microfluidic device surfaces. For example, 0.1-0.5% (e.g., 0.2%) polysorbate 20 (Tween 20®) may be used to improve lysis performance and mobility of the first combined droplet. Any non-ionic detergent with a large polar group could be substituted, such as octylphenol ethoxylate, wherein the ethoxylate group has an average length of at least 9 ethyloxide units, or at least 15, 20, 25, 30 or more ethyloxide units (e.g., Triton X-305 or Triton X-100), octylphenoxypolyethoxyethanol (e.g., NP-40).
Fragment genomic DNA (
The genomic DNA released by cell lysis was fragmented. The first combined droplet (generated in step 1120) was mixed with a third droplet containing double-stranded DNA cutting reagent to form a second combined droplet. Examples of DNA cutting reagent include a fragmentase (e.g., commercially available KAPA Fragmentase; NEBNext dsDNA Fragmentase). Alternatively, one or a mixture of endonucleases/restriction enzymes may be used.
The second combined droplet was incubated at 37° C. for 15 minutes or longer. Then, the fragmentation reaction was stopped by, for example, raising the temperature to 65° C. (thereby denaturing the DNA cutting reagent).
Modifications of fragmentation mix and ligation mix were developed specifically for use with the modified surfaces (SSRL1 or SSRL2) as described herein and below in Tables 3 and 4.
The droplet containing the double-stranded DNA cutting reagent included a surfactant. The surfactant varies depending on the reagent and the surface coating of the microfluidic device. For example, for SSRL1, TET surfactant was used (essentially no fouling was observed, even at high temperature); PEO-PPO block co-polymers (e.g., Pluronics F68, L31, and F127) and N-(1,3-bis(Glucopyranoside)propan-2-yl)-3-Butyl-3-Cyclohexylheptanamide (e.g., Cy-Tripglu (formerly called Tritop)) were also used successfully. For SSRL2, PEO-PPO block co-polymers (e.g., Pluronics F68, L31, F127) and TET surfactant both worked well.
Adding adapters to DNA fragments (
After a fragmentase (or mixture of restriction endonucleases) is used at step 1130, adapters are added to DNA fragments in a two-step process:
The first step is to generate 3′A nucleotide overhang at the ends of the DNA fragments. The second combined droplet (from step 1130) is merged with a fourth droplet containing a polymerase/A-tailing enzyme to form a third combined droplet. For example, the fourth droplet can include Taq polymerase, a suitable Taq buffer, and a mixture of all nucleotides. The third combined droplet is incubated for an appropriate time and temperature, e.g., 65° C. for 30 minutes. Polymerases other than Taq polymerase can be used (e.g., KAPA A-tailing mixture).
The second step is to ligate double-stranded adapters having a 5′ T nucleotide overhang at one or both ends. The third combined droplet (from step 1140A) is merged with a fifth droplet containing a ligase (and ATP) to form a fourth combined droplet. For example, the fifth droplet can include T4 ligase. The fourth combined droplet is incubated for appropriate time and temperature, e.g., 20° C. for 15 minutes. Ligases other than T4 can be used.
Each adapter can include a unique barcode, and/or a target sequence for amplification. Combinations of barcodes can be used with different samples so that each sample is uniquely labeled, as described herein and illustrated in
The droplet containing the polymerase/A-tailing mixture includes a surfactant. The surfactant varies depending on the surface coating of the microfluidic device. For example, 0.1-0.5% (e.g., about 0.2%) Cy-Tripglu (Tritop) was used successfully with the SSRL1 coating. With the SSRL2 coating, the surfactant from the previous steps can be sufficient. Alternatively, the same type of surfactant used in moving cell-containing droplets in prior step 1110 may be used, e.g., to maintain a constant overall concentration of surfactant.
Tagmentation (alternative with combined fragmentation and adapter addition) (
Alternatively, steps 1130 (fragmentation) and 1140 (adding adapters to DNA fragments) of
Barcoding and Tailing/ Bead Based Barcoding Protocols were developed to introduce barcodes to nucleic acid fragments, adapted to be modified to contain the barcodes. Barcoding can be performed using beads. The resulting amplification via qPCR demonstrated the ability to amplify via a PCR under thermal cycling conditions. An example of barcoding and tailing is described in Examples 2-B and
On-Chip DNA Fragment Amplification (
On-Chip amplification is performed as follows. The fourth combined droplet containing DNA fragments from step 1140B, or if tagmentation is performed, the third combined droplet prior to amplification is purified. The purified DNA droplet (or the fourth combined droplet from step 1140B) is merged with a sixth droplet containing an amplification mixture to form a fifth combined droplet. Then, temperature cycling on the fifth combined droplet is performed. For DNA amplification, a high-fidelity DNA polymerase (e.g., KAPA HiFi polymerase, or the like) is used. The times for each cycle may vary, including the time for temperature increase/decrease. The standard temperature cycle may include 95° C. for 70 seconds, 55° C. for 30 seconds, 72° C. for 50 seconds. Depending on the desired amount of amplification, temperature cycling can be performed with 4-15 cycles. In some embodiments, 4-6 cycles or 10-14 cycles are performed. In some embodiments, 12 cycles of thermal cycling are performed.
For DNA fragments from step 1140B, each primer may include a sequence complementary to an adapter target sequence and, optionally, a sequence that can be used for further amplification and/or sequencing (e.g., P5 and P7 sequences in primers available from Illumina). For DNA fragments produced by tagmentation, each primer may include a barcode sequence located between the adapter target sequence and the sequence useful for further amplification and/or sequencing.
The amplification mix includes a surfactant to prevent DNA and DNA polymerase from fouling surfaces. For example, 0.1%45% (or 0.2%) Tween-20 was found to be effective. Alternatively, 0.1%-0.5% (or 0.2%) of a PEO-PPO block co-polymer (e.g., Pluronic F68, Pluronic F127) or 0.1%-0.5% (or 0.2%) of 2,4,7,9-tetramethyl-5-decyne-4,7-diol ethoxylate (TET) can be used.
Subsequent Steps
Amplified DNA fragments were purified (
Bead Based Purification (
Elution (
Quantification. Protocols were developed to permit on-chip quantification. DNA was aliquoted and incubated with fluorescent dye for quantification (e.g., incubated for 3 minutes at room temperature). An example of quantification is described in Example 2-F.
Sequencing Results.
The KAPA Hyper Plus Workflow DNA library preparation protocol was adapted for use within a microfluidic device having an optoelectronic wetting configuration, as shown in Tables 2-4, below. Table 2 represents a general workflow, while Tables 3 and 4 show workflows that were optimized for microfluidic devices having SSRL1 and SSRL2 surface coatings, respectively.
Each adapter can include a unique barcode and/or a target sequence for amplification. Combinations of barcodes can be used with different samples so that each sample is uniquely labeled. As shown in
A combination of barcodes was used as follows: with one of Barcode 1, 2, or 3 on one side and one of Barcode 4, 5, 6, or 7 on the other side, a total of 12 distinct combinations of barcodes could be provided. As shown in
One example of bead-based barcoding during PCR for OEW library preparation is as follows. The first barcode was immobilized on beads (via streptavidin or biotin) to barcode each droplet/pool. The second barcode was provided in solution to barcode each chip/experiment to increase sequencing multiplexing possibilities. Additionally, P5 and P7 primers in solution in the primer mix (suppression PCR) can be added.
Examples of beads for use in barcording include QuantumPlex™M (which consists of five populations of ˜6 μm superparamagnetic microspheres encoded with different intensities of Starfire Red™, Item No. 252, Bangs), FSO6F Flash Red, FSO5F Flash Red, FSO6F Envy Green, FSO7F Dragon Green (Bangs), FH-10062-2 Purple (Spherotech), and 2008 Blue (Phosphorex).
The effects of surfactants on the cell lysis step was investigated. Lysis, fragmentation and ligation was conducted according to the KAPA protocols as described above in Example 2-A. 0.2-0.5% Tween-20 surfactant was included in the ligation mix.
Then, fragmented and ligated products were amplified off chip as follows. The droplet was brought up to 10 ul in volume with water. 8 ul of AMpure beads were used to clean the reaction. 8.2 ul of water was used to isolate DNA from beads. The isolated DNA were put into 20 μl PCR mix (2×10 μl) (which requires 15 cycles). In the PCR mix, 2 ul Illumina PCR primers (20 uM) and 8 ul of workflow elution were included. After PCR was conducted, the amplified DNA samples were collected and BioAnalyzer was run on them to investigate the quality of the DNA fragments.
The results from BioAnalyzer are as shown in
These results showed that while the protease alone may work for cell lysis, use of surfactants such as a polysorbate (polysorbate 20) improved efficiency and consistency in production of suitable sized products as the surfactant reduced interface interactions (among glass, oil, and surface area of the droplet) and thus decreases the chance of undesired absorption of DNA or enzymes.
Two different amplification methods where nucleic acids are tagmented (Nextera XT) or randomly fragmented and adapted (KAPA Hyper Plus) were modified to be suitable for the micro fluidic chip having a surface according to Surface #1 (SSRL1 coating) with fluorinated oil.
One of the protocols developed to amplify fragments derived from the tagmentation regime is as follows.
Nextera XT libraries were prepared off chip and quantified off chip to control for template amount. On-chip fragment amplification was conducted with 90 pg template per 20 nl of PCR mix droplet (4.5 ng/μl). Purification of PCR product was performed with 4 μl diluted exported droplet and 8 μl beads (AMPure purification kit) prior to quantification. Then, the eluted amount of 4 μl was aliquoted to 2 μl for fluorescence quantification (Qubit) and 1 μl for Bioanalyzer, and the quantification results were 0.785 ng/μl and 1.06 ng/μl, respectively, corresponding to amplified DNA amounts of 3.032 ng and 4.24 ng, respectively, indicating that on-chip amplification had occurred (
The on-chip PCR was performed on a droplet originally containing ˜20 cells, which was merged with a ˜50 nl droplet containing PCR mix (Trusight Rapid Capture kit (NLM +i5 +i7)). After 18 cycles, the combined droplets were exported and purified with 1.8× AMpure XP purification beads. The off-chip PCR was performed with a NPM PCR mix and 18 cycles, followed by purification with 1.8× AMpure XP beads. The resulting product was quantified to be 45 ng/μl by fluorescence quantification (Qubit). The high quantity of 45 ng/μl after the additional 18 cycles of PCR performed off chip show the utility of pre-amplification on the chip. Although amplification on chip is not necessary, it increases the amount of sample available for sequencing and, when used to add barcodes, facilitates the pooling of samples and related increases in sample recovery after cleaning off chip. While this example describes 18 cycles of on chip PCR, the advantages that come from increasing the amount of sample available and addition of barcodes (if needed) can be achieved with just a few on chip PCR cycles (e.g., 3 or more cycles, 3 to 10 cycles, 4 to 8 cycles, or 5 to 6 cycles.)
The above amplification method can be applied to provide whole genome analysis of an amplified tagmented library.
One example of the protocols developed to amplify fragments derived from the fragmentation/ligation regime is as follows.
A purified library from the KAPA workflow was prepared off-chip with fragments up to 400 bp in size, and droplets were prepared to include 10 pg DNA per 50 nl droplet. (1) An amplification mixture (KAPA PCR mix) and (2) the same amplification mix further combined with 1 mg/ml BSA and 0.2% Pluronic F68 surfactant was prepared and mixed with the DNA droplets off-chip, and the combined droplet was introduced into the microfluidic chip.
On-chip PCR was performed for 15 cycles, and the combined droplets containing the amplified DNA were exported. 50 ul of oil with the droplets were mixed with 100ul DNA column binding buffer, and the mixture was vortexed for 15 seconds and then spun in a centrifuge for 1 min. The aqueous phase of the mixture was added to the separation column, and DNA was isolated and quantified, the result of which is shown in Table 6. When the amplification mix did not contain surfactants, on-chip PCR showed no detectable yield. In contrast, when surfactants were included in the amplification mix, the yields increased significantly.
Further, the effect of Tween-20 surfactant on on-chip PCR yield was determined with the SSRL2 surface. PCR products were produced and quantified as described above.
As shown above in Table 7, as compared to off-chip controls, the yields were higher when a surfactant (Tween-20) was used. This result also shows that on-chip products had slightly higher average yield than off-chip controls. Using Pluronic F68 as the surfactant was also effective (not shown). The surfactant is thought to decrease molecular interactions at interfaces (cover surface, droplet-oil interface, substrate surface) and prevent high failure rate of on-chip PCR.
Methods for quantifying the amplified nucleic acids on chip were developed.
A DNA mix was prepared with a dsDNA ladder (Life Technologies 1kb plus ladder) in a reverse transcription buffer containing 0.2% 2, 4, 7, 9-Tetramethyl-5-decyne-4, 7-diol-ethoxylate (TET). DNA aliquots of 0 ng/μl, 1 ng/μl, 5 ng/μl, 10 ng/μl, and 30 ng/μl were loaded in the pens and were washed twice with water. A dsDNA dye (1/100 Quant-iT™ High Sensitive Assay, Invitrogen Cat# Q33120) in RT Buffer with 0.2% TET was loaded into the pens and the DNA aliquots were incubated for 3 minutes at room temperature.
An example of results of a cDNA QC of a library prepared using the electrowetting based lysis and barcoding is shown on
Lysis. Generally, cell lysis conditions will depend on whether DNA or RNA is desired. If RNA is desired, lysis may be performed at room temperature or at a temperature less than 50° C., if using a proteinase K lysis buffer. The lysis reaction may be stopped by addition of stop lysis reagents as is known in the art, which may obviate the need for a high temperature inactivation of proteinase K. Alternatively, other lysis buffers may be used that do not require heating or high temperature inactivation. Lysis procedures for obtaining DNA are discussed above in detail.
On-Chip qPCR. The ability to quantify PCR reagents and DNA samples within the microfluidic environment permitted quantitative polymerase chain reaction (qPCR) experiments to be successfully performed, as shown in
Further,
Amplification introducing barcodes.
Amplification on beads to introduce barcodes. protocols developed to introduce barcodes and/or primers by amplification on beads were described above (See
Purification. Methods of purifying the amplified nucleic acids can be performed as described above.
On-chip reverse transcription was performed as follows: 20 μl of 2× reaction mixture was prepared including 8 ul 5× RT buffer, 3 ul poly(d1) primer, 3 ul template switching oligonucleotide (TSO), 2 ul dNTPs, 1.8 ul reverse transcription enzyme, 1.8 ul 100 ml MgCl2, 0.4 ul TET (surfactant). This reaction mixture was combined on chip with an equal volume sized droplet containing 500 pg of OKT3 cDNA, 0.2% RNAseOUT™, and 0.2% TET. At this concentration, a 20 nl droplet is estimated to contain 10 pg of total RNA. Heat cycle was performed at 55° C. for 2 min (Dt annealing) and then 42° C. for 1 hour. Droplets were moved out of pen and 11 droplets were exported, 377 nL total. To visualize exported droplets, 2 ul of water containing phenol red dye was added to tube and spun down in centrifuge. The droplet turns bright red as the dye was mixed with the reverse transcription mix. 1 ul of droplet was added to a first cDNA amplification PCR product. 1.3 ul was added to a second cDNA amplification PCR product. 20 cycles of SMART-sequence amplification were performed.
The amplified product was recovered by Quibit. The yield from the first amplification was 1.53 ng of cDNA, and the yield from the second amplification was 3.13 ng of cDNA. To visualize the cDNA quality the first test, PCR was performed from each amplification product for the presence of mouse Kappa chain. As shown in
This example concerns improvements in temperature control for a microfluidic device undergoing temperature shifts driven by a Peltier thermoelectric device. The Peltier used in this experiment was DigiKey part number 102-1674-ND (see the www.digikey.com website at /product-detail/en/cui-inc/CP60333/102-1674-ND/1747366 for details). The specs indicate a maximum power draw of 50W to 90W.
Initial experiments used a PID control loop algorithm to determine the power output value for the Peltier based on target temperature and current temperature as measured by a thermistor. It was observed that the actual temperature of the microfluidic device could overshoot the target temperature both during heating and cooling (not shown), which could compromise performance, e.g., both at high-temperature steps such as denaturation steps (in that excessive heat could reduce polymerase activity or increase degradation of the hydrophobic layer) and lower temperature steps such as primer annealing (in that lower temperature could promote mispriming and loss of specificity). See
To address temperature overshooting, the three-phase temperature control procedure described in the Systems section above was developed, i.e., comprising setting the power output to a first value if the difference between the target temperature and the thermistor-measured temperature is larger than N; setting the power output to a second value lower than the first value if the difference between the target temperature and the thermistor-measured temperature is equal to or smaller than N and larger than M; and determining the power output by a proportionate-integral-derivative (PID) loop controller with the thermistor-measured temperature as an input if the difference between the target temperature and the thermistor-measured temperature is smaller than or equal to M, where M may be in the range of 7° C. to 13° C. or 5° C. to 15° C. and N may be in the range of 2° C. to 4° C. or 1° C. to 5° C. The second value was determined from calibration data correlating target temperatures to power output values for the Peltier. Calibration data for a representative system are shown below. The calibration data were determined by equilibrating the system at each progressively higher power output value and measuring the resulting temperature from the thermocouple of a calibration chip, and are intended for use in heating steps. A corresponding data set for cooling steps was also generated by starting at a high (i.e., hot) power output value and progressively reducing it (not shown). Because individual systems may differ slightly in details such as efficiency of heat transfer between a microfluidic device and the Peltier, it can be advisable to generate calibration data for a particular system. Power output values corresponding to temperatures between those shown in Table 8 can be determined using linear interpolation or other known curve-fitting methods.
Results obtained in a heating step toward 95° C. and a cooling step toward 55° C. using the three-phase temperature control procedure are shown in
Results from a more complex series of temperature shifts are shown in
Data from a further experiment using a similar temperature control procedure wherein M was 3° C. and N was 10° C. are shown in
It is expected that similar results would be obtained within the ranges of 10° C. plus or minus 5° C. for N and 3° C. plus or minus 2° C. for M.
The embodiments disclosed herein include the following:
a droplet actuation surface, a substrate having a dielectric layer and a first electrode configured to be connected to an AC voltage source, and a second electrode configured to be connected to the AC voltage source,
wherein the dielectric layer is electrically coupled to the first electrode,
wherein the droplet actuation surface comprises a hydrophobic layer covalently bonded to the dielectric layer, and
wherein, when the first electrode and the second electrode are connected to opposing terminals of the AC voltage source, the substrate is capable of applying an electrowetting force to aqueous droplets in contact with the droplet actuating surface.
wherein the substrate and the cover are substantially parallel to one another and joined together by the spacing element so as to define an enclosure configured to hold a liquid,
wherein the droplet actuation surface defines, in part, the enclosure, and
wherein the cover comprises the second electrode and a surface of the second electrode defines, in part, the enclosure.
wherein is a surface of the dielectric layer;
V is —P(O)(OY)W— or —Si(OZ)2W—;
W is —O—, —S—, or —NH— and connects to the surface;
Z is a bond to an adjacent silicon atom attached to the surface or is a bond to the surface;
Y is a bond to an adjacent phosphorus atom attached to the surface or is a bond to the surface;
R is hydrogen or fluorine;
M is hydrogen or fluorine;
h is 0 or an integer of 2 or 3, j is 1, and k is 0 or 1;
m is 0 or an integer of 1 to 20;
n is 0 or an integer of 1 to 20;
the sum of (n+[(h+j)·k]+m) is an integer of 11 to 25;
when k is 1, then m is at least 2 and M is hydrogen; and
when k is 0 and R is fluorine, then m is at least 2 and M is hydrogen.
wherein is a surface of the dielectric layer;
V is —P(O)(OY)W— or —Si(OZ)2W—;
W is —O—, —S—, or —NH— and connects to the surface;
Z is a bond to an adjacent silicon atom attached to the surface or is a bond to the surface;
Y is a bond to an adjacent phosphorus atom attached to the surface or is a bond to the surface;
R is hydrogen or fluorine;
M is hydrogen or fluorine;
h is 0 or an integer of 2 or 3; j is 1; and k is 0 or 1;
m is 0 or an integer of 1 to 20;
n is 0 or an integer of 1 to 20;
the sum of (n+[(h+j)·k]+m) is an integer of 11 to 25;
when k is 1, then m is at least 2 and M is hydrogen; and
when k is 0 and R is fluorine, then m is at least 2 and M is hydrogen.
disposing a first droplet of aqueous medium upon a droplet actuation surface of the microfluidic device, wherein the first droplet comprises one or more biological cells, and wherein the micro fluidic device further comprises
merging the first droplet with a second droplet of aqueous medium to form a first combined droplet, wherein the second droplet comprises a cell lysing agent;
incubating the first combined droplet upon the droplet actuation surface for a first period of time sufficient to lyse the one or more biological cells; and
inactivating the cell lysing agent.
disposing a first droplet of aqueous medium upon a droplet actuation surface of the microfluidic device, wherein the first droplet comprises one or more biological cells, and wherein the micro fluidic device further comprises
merging the first droplet with a second droplet of aqueous medium to form a first combined droplet, wherein the second droplet comprises a cell lysing agent;
incubating the first combined droplet upon the droplet actuation surface for a first period of time sufficient to lyse the one or more biological cells; and
inactivating the cell lysing agent.
disposing a first droplet of aqueous medium upon a droplet actuation surface of the microfluidic device, wherein the first droplet comprises one or more biological cells, and wherein the micro fluidic device further comprises
merging the first droplet with a second droplet of aqueous medium to form a first combined droplet, wherein the second droplet comprises a cell lysing agent;
incubating the first combined droplet upon the droplet actuation surface for a first period of time sufficient to lyse the one or more biological cells; and
inactivating the cell lysing agent.
merging the second combined droplet with a fourth droplet of aqueous medium to form a third combined droplet, wherein the fourth droplet comprises a DNA polymerase having A-tailing activity; and
adjusting the temperature of the microfluidic device to a temperature of about 60° C. to about 70° C. (e.g., about 62° C. to about 68° C., or about 65° C.), optionally for at least about 15 minutes (e.g., about 15 to 45 minutes, about 20 to about 40 minutes, about 25 to about 35 minutes, or about 30 minutes).
adjusting the temperature of the microfluidic device to a temperature of about 15° C. to about 25° C. (e.g., about 18° C. to about 22° C., or about 20° C.);
merging the third combined droplet with a fifth droplet to form a fourth combined droplet, wherein the fifth droplet comprises a ligase and oligonucleotide adapters; and
optionally, incubating the fourth combined droplet for a period of at least about 10 minutes (e.g., about 10 to about 20 minutes (e.g., about 12 to about 18 minutes, or about 15 minutes).
merging the first combined droplet with a third droplet of aqueous medium to form a second combined droplet, wherein the third droplet comprises a reverse transcriptase; and
incubating the second combined droplet upon the droplet actuation surface for a period of time sufficient to reverse transcribe RNA released by the lysed one or more biological cells.
adjusting the temperature of the microfluidic device to a temperature of about 50° C. to about 60° C. (e.g., about 52° C. to about 58° C., or about 55° C.), for at least about 1 minute (e.g., about 1 to 5 minutes, about 1 to about 3 minutes, or about 2 minutes); and
adjusting the temperature of the microfluidic device to a temperature of about 37° C. to about 45° C. (e.g., about 40° C. to about 43° C., or about 42° C.), for at least about 45 minutes (e.g., at least about 50, about 55, about 60 minutes, or more).
merging the second combined droplet with a fourth droplet of aqueous medium to form a third combined droplet, wherein the fourth droplet comprises a nucleic acid polymerase, and a buffer and precursors (e.g., nucleotides, primers, etc.) that support a polymerase activity of the nucleic acid polymerase; and
incubating the third combined droplet upon the droplet actuation surface, under conditions that promote amplification of cDNA present.
merging the second combined droplet with a fourth droplet of aqueous medium to form a third combined droplet, wherein the fourth droplet comprises a nucleic acid polymerase, and a buffer and precursors (e.g., nucleotides, primers, etc.) that support a polymerase activity of the nucleic acid polymerase; and
incubating the third combined droplet upon the droplet actuation surface, under conditions that promote amplification of fragmented DNA present.
merging the third combined droplet with a sixth droplet of aqueous medium to form a fourth combined droplet, wherein the sixth droplet comprises a nucleic acid polymerase, and a buffer and precursors (e.g., nucleotides, primers, etc.) that support a polymerase activity of the nucleic acid polymerase; and
incubating the fourth combined droplet upon the droplet actuation surface, under conditions that promote amplification of fragmented DNA present.
amplifying the nucleic acid fragments or cDNA, wherein amplifying comprises merging the droplet comprising the nucleic acid fragments or cDNA with a droplet comprising an amplification mixture and a surfactant (optionally wherein the surfactant is a polysorbate surfactant having a molecular weight of at least 1000 daltons (e.g., polysorbate 20), optionally at a concentration ranging from 0.1% to 0.5% (or 0.15% to 0.3%), or a surfactant as recited in any one of embodiments 98-105, thereby forming a combined amplification droplet; and
incubating the combined amplification droplet under conditions that promote amplification.
disposing a first droplet of aqueous medium upon a droplet actuation surface of the microfluidic device, wherein the first droplet comprises nucleic acid (e.g., nucleic acid fragments), and wherein the microfluidic device further comprises
merging the first droplet with a second droplet of aqueous medium to form a combined droplet, wherein the second droplet comprises a nucleic acid polymerase, and wherein the combined droplet comprises a buffer and precursors (e.g., nucleotides, primers, etc.) that support a polymerase activity of the nucleic acid polymerase; and
incubating the combined droplet upon the droplet actuation surface, under conditions that promote amplification of the nucleic acid originating from the first droplet.
a support configured to hold and operatively couple with a microfluidic device, the support comprising:
In case of any contradiction or conflict between material incorporated by reference and the expressly described content provided herein, the expressly described content controls.
The foregoing written specification is considered to be sufficient to enable one skilled in the art to practice the embodiments. The foregoing description and Examples detail certain embodiments and describes the best mode contemplated. It will be appreciated, however, that no matter how detailed the foregoing may appear in text, the embodiment may be practiced in many ways and should be construed in accordance with the appended claims and any equivalents thereof.
This application is a continuation of International Patent Application No. PCT/US2018/029648, filed Apr. 26, 2018, which claims priority from U.S. Provisional Application No. 62/490,534, filed Apr. 26, 2017, and U.S. Provisional Application No. 62/490,596, filed Apr. 26, 2017, the contents of each of which are incorporated herein by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62490596 | Apr 2017 | US | |
| 62490534 | Apr 2017 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/US2018/029648 | Apr 2018 | US |
| Child | 16661310 | US |
