Patent Application
20100282608
The invention relates to droplet actuation devices, and in particular to specialized structures for conducting droplet operations.
Droplet actuators are used to conduct a wide variety of droplet operations. A droplet actuator typically includes two substrates separated by a gap. The substrates are associated with electrodes for conducting droplet operations. The gap includes a filler fluid that is immiscible with the fluid that is to be manipulated on the droplet actuator. The formation and movement of droplets in the gap is controlled by electrodes for conducting a variety of droplet operations, such as droplet transport and droplet dispensing. At least one of the surfaces is typically made from a transparent material, such as a glass top substrate. Among other things, when glass is used, adding features to the glass, such as openings for loading fluid into the gap, can be complex and expensive. There is a need for alternative droplet actuator structures that are easier and less expensive to manufacture while providing the same or better functionality as glass top substrates.
The invention provides a modified droplet actuator. The droplet actuator generally includes a base substrate and a top substrate separated to form a gap. One or both substrates, but typically the base substrate, includes electrodes configured for conducting droplet operations in the gap. The top substrate may include a first portion coupled to second portion, where the second portion includes one or more openings establishing a fluid path extending from an exterior of the droplet actuator and into the gap.
The first portion may include a more uniformly planar surface exposed to the gap than the second portion. In some embodiments, the first portion is more transparent than the second portion, or the first portion is transparent and the second portion is not. In one embodiment the first portion is substantially transparent, and the second portion is substantially opaque. In another embodiment, the first portion harder than the second portion. In still another embodiment, the first portion is more thermally stable than the second portion. In yet another embodiment, the first portion is more resistant to damage caused by temperature fluctuation than the second portion.
The invention also provides a droplet actuator including a base substrate and a top substrate separated to form a gap, wherein the base substrate includes electrodes configured for conducting droplet operations in the gap; and the top substrate includes a glass portion coupled to a non-glass portion, where the non-glass portion includes one or more openings establishing a fluid path extending from an exterior of the droplet actuator and into the gap. The non-glass portion may, in some embodiments, include or be manufactured from a plastic or resin portion. In some cases, the non-glass portion includes a frame into which the glass portion is inserted.
The fluid path may be arranged to flow fluid into an actual or virtual reservoir associated with one or more reservoir electrodes associated with the base substrate. The fluid path may be arranged to flow fluid into proximity with one or more of the electrodes.
In some embodiments, the glass portion does not include openings therein. In some embodiments, the non-glass portion overlaps the glass portion, and an aperture is provided in the non-glass portion for providing a sensing path from the gap, through the glass portion, through the aperture to an exterior of the droplet actuator. A fitting may be provided in association with the aperture for fitting a sensor onto the droplet actuator.
In some embodiments, a handle is provided, extending from the glass portion and arranged to facilitate user handling of the droplet actuator. In other embodiments, the non-glass portion further includes a hinged cover arranged to seal the openings when the hinged cover is in a closed position. The cover may include one or more dried reagents associated therewith, such that when fluid is present in one or more of the openings, and the cover is closed, the dried reagents contact the fluid and are combined therewith to form fluid reagents.
In another embodiment, the non-glass portion overlaps the glass portion; and one or more of the openings extends through the non-glass portion, through the glass portion, and into the gap. In some embodiments, the opening extending through the non-glass portion is configured as a fluid reservoir.
The invention also provides a droplet actuator including a base substrate and a top substrate separated to form a gap, wherein the (a) base substrate includes electrodes configured for conducting droplet operations in the gap; and an opening forming a fluid path from an exterior of the droplet actuator into the gap; and (b) the top includes a top substrate electrode arranged opposite the opening such that fluid flowing into the gap through the opening flows into proximity with the top substrate electrode.
The invention also includes methods of loading a fluid onto a droplet actuator. The methods generally include providing a droplet actuator of the invention and loading a fluid through the opening and into the gap.
The invention also includes methods of assembling a droplet actuator of the invention. The methods generally coupling the glass portion to the non-glass portion of the top substrate, and assembling the top substrate with the bottom substrate to form a gap therebetween suitable for conducting droplet operations.
Finally, the invention includes methods of conducting a droplet operation. The methods generally include providing a droplet actuator of the invention; loading a liquid onto the droplet actuator into proximity with one or more electrodes; and using the one or more electrodes to conduct the droplet operation.
Other aspects of the invention will be apparent from the ensuing detailed description of the invention.
As used herein, the following terms have the meanings indicated.
“Activate” with reference to one or more electrodes means effecting a change in the electrical state of the one or more electrodes which results in a droplet operation.
“Droplet” means a volume of liquid on a droplet actuator that is at least partially bounded by filler fluid. For example, a droplet may be completely surrounded by filler fluid or may be bounded by filler fluid and one or more surfaces of the droplet actuator. Droplets may, for example, be aqueous or non-aqueous or may be mixtures or emulsions including aqueous and non-aqueous components. Droplets may take a wide variety of shapes; nonlimiting examples include generally disc shaped, slug shaped, truncated sphere, ellipsoid, spherical, partially compressed sphere, hemispherical, ovoid, cylindrical, and various shapes formed during droplet operations, such as merging or splitting or formed as a result of contact of such shapes with one or more surfaces of a droplet actuator.
“Droplet Actuator” means a device for manipulating droplets. For examples of droplets, see U.S. Pat. No. 6,911,132, entitled “Apparatus for Manipulating Droplets by Electrowetting-Based Techniques,” issued on Jun. 28, 2005 to Pamula et al.; U.S. patent application Ser. No. 11/343,284, entitled “Apparatuses and Methods for Manipulating Droplets on a Printed Circuit Board,” filed on filed on Jan. 30, 2006; U.S. Pat. No. 6,773,566, entitled “Electrostatic Actuators for Microfluidics and Methods for Using Same,” issued on Aug. 10, 2004 and U.S. Pat. No. 6,565,727, entitled “Actuators for Microfluidics Without Moving Parts,” issued on Jan. 24, 2000, both to Shenderov et al.; Pollack et al., International Patent Application No. PCT/US2006/047486, entitled “Droplet-Based Biochemistry,” filed on Dec. 11, 2006, the disclosures of which are incorporated herein by reference. Methods of the invention may be executed using droplet actuator systems, e.g., as described in International Patent Application No. PCT/US2007/009379, entitled “Droplet manipulation systems,” filed on May 9, 2007. In various embodiments, the manipulation of droplets by a droplet actuator may be electrode mediated, e.g., electrowetting mediated or dielectrophoresis mediated.
“Droplet operation” means any manipulation of a droplet on a droplet actuator. A droplet operation may, for example, include: loading a droplet into the droplet actuator; dispensing one or more droplets from a source droplet; splitting, separating or dividing a droplet into two or more droplets; transporting a droplet from one location to another in any direction; merging or combining two or more droplets into a single droplet; diluting a droplet; mixing a droplet; agitating a droplet; deforming a droplet; retaining a droplet in position; incubating a droplet; heating a droplet; vaporizing a droplet; condensing a droplet from a vapor; cooling a droplet; disposing of a droplet; transporting a droplet out of a droplet actuator; other droplet operations described herein; and/or any combination of the foregoing. The terms “merge,” “merging,” “combine,” “combining” and the like are used to describe the creation of one droplet from two or more droplets. It should be understood that when such a term is used in reference to two or more droplets, any combination of droplet operations sufficient to result in the combination of the two or more droplets into one droplet may be used. For example, “merging droplet A with droplet B,” can be achieved by transporting droplet A into contact with a stationary droplet B, transporting droplet B into contact with a stationary droplet A, or transporting droplets A and B into contact with each other. The terms “splitting,” “separating” and “dividing” are not intended to imply any particular outcome with respect to size of the resulting droplets (i.e., the size of the resulting droplets can be the same or different) or number of resulting droplets (the number of resulting droplets may be 2, 3, 4, 5 or more). The term “mixing” refers to droplet operations which result in more homogenous distribution of one or more components within a droplet. Examples of “loading” droplet operations include microdialysis loading, pressure assisted loading, robotic loading, passive loading, and pipette loading. In various embodiments, the droplet operations may be electrode mediated, e.g., electrowetting mediated or dielectrophoresis mediated.
“Filler fluid” means a fluid associated with a droplet operations substrate of a droplet actuator, which fluid is sufficiently immiscible with a droplet phase to render the droplet phase subject to electrode-mediated droplet operations. The filler fluid may, for example, be a low-viscosity oil, such as silicone oil. Other examples of filler fluids are provided in International Patent Application No. PCT/US2006/047486, entitled, “Droplet-Based Biochemistry,” filed on Dec. 11, 2006; and in International Patent Application No. PCT/US2008/072604, entitled “Use of additives for enhancing droplet actuation,” filed on Aug. 8, 2008.
The terms “top” and “bottom,” when used, e.g., to refer to the top and bottom substrates of the droplet actuator, are used for convenience only; the droplet actuator is generally functional regardless of its position in space.
The terms “top” and “bottom” are used throughout the description with reference to the top and bottom substrates of the droplet actuator for convenience only, since the droplet actuator is functional regardless of its position in space.
When a liquid in any form (e.g., a droplet or a continuous body, whether moving or stationary) is described as being “on”, “at”, or “over” an electrode, array, matrix or surface, such liquid could be either in direct contact with the electrode/array/matrix/surface, or could be in contact with one or more layers or films that are interposed between the liquid and the electrode/array/matrix/surface.
When a droplet is described as being “on” or “loaded on” a droplet actuator, it should be understood that the droplet is arranged on the droplet actuator in a manner which facilitates using the droplet actuator to conduct one or more droplet operations on the droplet, the droplet is arranged on the droplet actuator in a manner which facilitates sensing of a property of or a signal from the droplet, and/or the droplet has been subjected to a droplet operation on the droplet actuator.
The invention provides a droplet actuator with improved features for loading fluid into the gap. In certain embodiments, the droplet actuator includes a top substrate that combines glass with one or more other materials that are easier to manufacture. Examples of such materials include resins and plastics. One such embodiment includes a top substrate including a glass substrate portion and a plastic portion. The glass substrate portion covers the droplet operations area of the droplet actuator, providing a flat, smooth surface for facilitating effective droplet operations. The plastic portion has one or more openings that provide a fluid path from an exterior locus into the gap of the droplet actuator. The fluid path facilitates loading of fluid into the gap of the droplet actuator.
An alternative embodiment of the invention provides a droplet actuator with one or more openings in the bottom substrate or substrate. Various embodiments of the invention may reduce or eliminate the need to form openings in the glass portion of a droplet actuator, avoiding a complex and costly manufacturing step. Still other embodiments avoid the use of glass altogether.
It should also be noted that in various embodiments, the non-glass portion may include multiple kinds of plastics rather than a glass/non-glass construction. For example, in the various glass/non-glass embodiments, one plastic may be substituted for the glass component and a second plastic may be used for the non-glass components. This approach may be employed to, among other things, take advantage of different optical properties (e.g., opaque for reservoirs/clear over electrodes or over detection zones) mechanical properties (flat, hard, planar, precise over electrodes/cheap, easy to mold or machine for fluid passages into reservoirs) or thermal properties (high T over electrodes for film deposition or PCR/cheaper low T for wells), surface properties and the like. In yet another alternative embodiment, the glass portion may be replaced with or coated with a metal foil and a non-glass material may be provided in regions where fluid passages into the droplet actuator are desired, for ease of manufacture.
7.1 Loading Mechanisms Using a Modified Top Substrate
Droplet actuator 100 includes a top substrate 110 that combines a glass portion with a second material, such as resin or plastic. In one embodiment, the top substrate 110 is formed of a glass substrate 114, the perimeter of which is partially or completely surrounded by a non-glass (e.g., plastic or resin) frame 118. The frame 118 includes one or more openings 122 forming a fluid path from an exterior of the droplet actuator 100 into the gap 132. In some embodiments, one or more of the openings 122 may provide a fluid path extending from the exterior of the droplet actuator 100 into an actual or virtual reservoir associated with one or more reservoir electrodes 134. In other embodiments, one or more of the openings 122 may provide a fluid path that is not aligned with or associated with any electrode or with any specialized electrode, such as a reservoir electrode.
Additionally, droplet actuator 100 includes a bottom substrate 126. The bottom substrate 126 includes an associated arrangement of electrodes 130 for performing droplet operations. Electrodes 130 may, for example, be covered with a hydrophobic insulator to permit manipulation of the liquid by electrowetting. The bottom substrate may also include one or more reservoir electrodes 134 for use in dispensing fluid from the reservoir. Bottom substrate 126 may, for example, be made using printed circuit board (PCB) technology or semiconductor manufacturing technology. Top substrate 110 and bottom substrate 126 are separated from one another to form a gap for conducting droplet operations.
The area of glass substrate 114 of top substrate 110 may be selected to cover the active droplet manipulation area of droplet actuator 100. In one example, the area of glass substrate 114 may substantially cover the arrangement of electrodes 130. The locations of openings 122 of frame 118 may correspond with locations of the one or more reservoir electrodes 134. In one embodiment, one or more reservoir electrodes is positioned at the periphery of glass substrate 114 for drawing a quantity of fluid 138 through the openings 122 into droplet actuator 100, e.g., as shown in
Glass substrate 114 may be transparent. Ideally, glass substrate 114 is as thin as is practical for providing optimal droplet detection capabilities. Frame 118 may, in some embodiments, be opaque and may be substantially the same thickness or thicker than glass substrate 114. A thick frame 118 may facilitate including fluid reservoirs or wells associated with openings 122 to contain a volume of fluid. Because openings 122 are formed within frame 118, glass substrate 114 may be manufactured without the need for forming openings therein. As a result, the added cost and complexity of forming openings in a glass top substrate may be reduced, preferably entirely avoided. By contrast, the process for forming openings, such as fluid reservoirs 122, in a plastic structure, such as frame 118, may be simple and inexpensive. In one embodiment, the total amount of glass required in the device is minimized by only using glass where the flatness, and optical qualities are required.
7.2 Top Substrate Assemblies
In one embodiment,
In another embodiment,
In yet another embodiment,
Referring again to
Glass substrate 614 further includes one or more openings 626 that correspond to one or more fluid reservoirs 632 within frame 618, as shown in
In this embodiment, because of the structural support that is provided by non-glass frame 618, the thickness of glass substrate 614 may be minimized, which allows the glass drilling process to be simplified. In order to facilitate easy loading or to provide reservoirs of larger fluid capacity, fluid reservoirs 632 of frame 618 may be larger than openings 626 of glass substrate 614. Additionally, the walls of fluid reservoirs 632 of frame 618 may have any of a variety of configurations, such as vertical walls or tapered (e.g., to form a conical shape) from a large opening to the smaller openings 626 of glass substrate 614. Forming such shapes in glass would be difficult, but is readily achieved using materials such as plastic or resins. Additionally, frame 618 may be provided having any useful thickness, thereby providing any useful fluid capacity via reservoirs 632.
In yet another embodiment, any of the foregoing embodiments may replace the glass portion with a molded material, such as a plastic or resin. Further, any of the foregoing embodiments may be made as a single plastic or resin component, rather than as glass/non-glass components.
In yet other embodiments, the top substrate may include one or more optical elements formed therein. For example, the optical element may include a lens and/or a diffraction gradient. The optical element may be configured to redirect, or otherwise modify, light to or from a droplet, fluid or surface of a droplet actuator. The optical element may be a modification in a surface of the top substrate or a coating adhered to or layered on a surface of the top substrate.
In one embodiment, the invention provides a top or bottom substrate that includes optical surface patterning. The optical surface patterning may be provided in a glass or non-glass portion of the top or bottom substrate. The top or bottom substrate may itself be glass or a combination of glass/non-glass. The optical surface patterning may, for example, introduce a diffractive optical element to the modified substrate. In one embodiment, the diffractive optical element introduces surface features on the same order of magnitude as the wavelength of light (micrometers or smaller) used for detection purposes. The optical surface patterning may be selected so that diffractive effects dominate refractive effects. In this manner, the microstructure of the optical surface patterning breaks up the light wave in a manner which produces interference patterns. The interference patterns can be evaluated to determine the shape of the output waveform.
7.3 Loading Mechanism in a Bottom Substrate
In this example, at least one opening 730 is provided in the second substrate, e.g., as shown in
In operation, droplet actuator 700 may be held in an inverted orientation, such as shown in
7.4 Combined Cartridge/Sample Collection Device
The modified substrates of the invention may also be used to provide sample collection functionality to a droplet actuator cartridge. For example, the top or bottom substrate may be associated with a syringe for sampling a liquid, such as blood or water. The syringe collection chamber may itself serve as liquid reservoir on the top or bottom substrate of the droplet actuator. In this embodiment, the top or bottom substrate includes or is associated with a fluid path from the gap between the substrate into the syringe collection chamber. Liquid from the collection chamber flows through the fluid path into proximity to one or more droplet operations electrodes, where it can be subjected to one or more droplet operations. Other embodiments may include simple sample collection tubes or catheters for introducing liquid from an exterior source into a droplet actuator for analysis.
In another embodiment, the droplet actuator may be configured to serve as a combination forensic sample collection tube and analysis cartridge. Microfluidic analysis can be performed either in the field, e.g., at the point of sample collection, or in a central lab. This configuration provides a quick test result while maintaining the bulk of the sample in pristine condition for further forensic testing. Follow-up testing for evidentiary purposes can then be performed later on the same sample using conventional (i.e., legally-accepted) techniques. In a related embodiment, the droplet actuator includes a break-away sample storage component so that the sample can be preserved in a more compact form.
7.5 Fluids
For examples of fluids that may be subjected to the loading operations and droplet operations using the modified droplet actuators of the invention, see the patents listed in International Patent Application No. PCT/US 06/47486, entitled, “Droplet-Based Biochemistry,” filed on Dec. 11, 2006. In some embodiments, the fluid includes a biological sample, such as whole blood, lymphatic fluid, serum, plasma, sweat, tear, saliva, sputum, cerebrospinal fluid, amniotic fluid, seminal fluid, vaginal excretion, serous fluid, synovial fluid, pericardial fluid, peritoneal fluid, pleural fluid, transudates, exudates, cystic fluid, bile, urine, gastric fluid, intestinal fluid, fecal samples, fluidized tissues, fluidized organisms, biological swabs and biological washes. In some embodiment, the fluid includes a reagent, such as water, deionized water, saline solutions, acidic solutions, basic solutions, detergent solutions and/or buffers. In other embodiments, the fluid includes a reagent, such as a reagent for a biochemical protocol, such as a nucleic acid amplification protocol, an affinity-based assay protocol, a sequencing protocol, and/or a protocol for analyses of biological fluids.
7.6 Method of making and Loading a Droplet Actuator of the Invention
A method of making a droplet actuator that includes a combination glass/non-glass top substrate includes, but is not limited to, the steps of (1) forming a bottom substrate from, for example, a PCB that includes transport electrodes and also one or more reservoir electrodes at its periphery; (2) forming a glass substrate the corresponds to the active electrowetting area of the bottom substrate of the droplet actuator; (3) forming a non-glass (e.g., plastic or resin) frame or substrate, to which the glass substrate may be coupled, and wherein the frame or substrate includes one or more fluid paths for introducing fluid into the gap; (4) assembling the bottom substrate and top substrate one to another to form the gap. Loading may involve providing a quantity of fluid through the fluid path into the gap. Where the fluid being loaded is a sample or reagent, the fluid may be loaded into proximity with an electrode so that droplet operations may be conducted using the fluid.
The foregoing detailed description of embodiments refers to the accompanying drawings, which illustrate specific embodiments of the invention. Other embodiments having different structures and operations do not depart from the scope of the present invention. This specification is divided into sections for the convenience of the reader only. Headings should not be construed as limiting of the scope of the invention. The definitions are intended as a part of the description of the invention. It will be understood that various details of the present invention may be changed without departing from the scope of the present invention. Furthermore, the foregoing description is for the purpose of illustration only, and not for the purpose of limitation, as the present invention is defined by the claims as set forth hereinafter.
This application claims priority to U.S. Patent Application No. 60/969,757, filed on Sep. 4, 2007, entitled “Improved droplet actuator loading”; and U.S. Patent Application No. 60/980,785, filed on Oct. 18, 2007, entitled “Droplet actuator with improved top plate”; the entire disclosures of which is incorporated herein by reference.
This invention was made with government support under NNJ06JD53C awarded by the National Aeronautics and Space Administration of the United States. The United States Government has certain rights in the invention.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US2008/075160 | 9/4/2008 | WO | 00 | 7/9/2010 |
| Number | Date | Country | |
|---|---|---|---|
| 60969757 | Sep 2007 | US | |
| 60980785 | Oct 2007 | US |
