Patent Application
20230294093
At micro volumes, fluids can behave differently from conventional fluid dynamics. It has been observed that mixing two micro-volumes of fluids is not convective as in bulk fluids; rather, they may not mix at all and can flow in a laminar fashion when bought together in a channel. The movement can be characterized by the ratio of inertial to viscous forces on fluids, namely, via the Reynolds number (Re). Electrowetting is a change in the wettability of a fluid via the application of an applied electric potential. Electrowetting has two types: direct electrowetting (where the fluid is in direct contact with the electrode) and electrowetting on dielectric (EWOD) (where an insulating layer is employed between the electrode and fluid).
Sample preparation can be very time-consuming and costly, particularly when the application employs many reagents, which is often the case for many medical diagnostic applications. The complexity of human-involved sample preparations also requires sophisticated lab equipment for dispensing and mixing. Microfluidic technologies, such as Electro-wetting on Dielectric, offer many advantages to the Point-of-Care (POC) devices through lower reagent use and smaller size. Additionally, Point-of-Care devices offer the unique potential to conduct tests outside of the laboratory.
While electro-wetting on dielectric (EWOD) microfluidics, direct electrowetting, and digital microfluidics has been shown to be an effective way to move and mix liquids enabling many PoC devices, much of the research surrounding these lab-on-a-chip microfluidic systems are focused on droplet control or a specific new application at the device level using the EWOD technology. Often in these experiments, the supporting systems required for operation are benchtop equipment such as function generators, power supplies, and personal computers.
There is a benefit and/or a need to improve microfluidics devices and their usage.
An exemplary system and method are disclosed for a digital microfluidic chip cartridge and system configured for electro-wetting on dielectric (EWOD) microfluidic operations and experimental analysis. The exemplary portable lab-on-a-chip devices and systems can be configured to execute complex assays such as DNA isolation employing integrated sensors and electronics that can analyze results. The EWOD or digital microfluidic cartridge can be configured with customizable assays having preloaded reagents targeted specifically for a given assay that can be used in an analysis in the field (i.e., point of care, i.e., not in a central laboratory) using a disposable or recyclable assay cartridge system. The cartridge and portable instrument can operate on specific instructions based on the algorithm intended for the assay.
The portable instrument can be fully self-contained, having a driving circuit configured to actuate the conductive tiles to move or mix the fluid along a fluidic plate. The cartridge device and associated system may have local and system-level self-testing circuit operations configured to assess operative contact between a conductive tile array and driving circuits. The EWOD or digital microfluidic cartridge may include field-enhancing structures to improve the reliability of the electro-wet or digital microfluidic operations. The EWOD or digital microfluidic cartridge may employ a hydrophobicity-effect-based micro-valve that can operate purely with electrical actuation and without pneumatics, reducing the complexity, cost, and reliability of the portable instrument.
In an aspect, a system is disclosed comprising a base system and a cartridge couplable to the base system. The cartridge includes: a housing; a microfluidic electrode assembly comprising: a fluidic plate (e.g., microfluidic plate) having two or more mixing/testing regions; a set of conductive tiles disposed along the fluidic plate that connects between the two or more mixing/testing regions, wherein the set of conductive tiles (e.g., pads) terminates at a set of a corresponding conductive-tile array located at an interface region on the fluidic plate; a self-testing circuit (e.g., disposed on a separate electronic board or disposed on the fluidic plate) having electronics configured to assess operative contact between (i) the conductive-tile array and (ii) driving circuits configured to actuate the set of conductive tiles to move or mix fluid along the fluidic plate.
In some embodiments, the system further includes at least one sensing tile (e.g., sensor) disposed along the fluidic plate adjacent to or integrated with the set of conductive tiles, wherein the at least one sensing tile terminates either (i) at the set of a corresponding conductive-tile array or (ii) a second set of a conductive-tile array, the self-testing circuit being configured to also assess operative contact of the conductive-tile array associated with the sensing tile.
In some embodiments, the system further includes a biosensor (e.g., electrochemical, impedimetric, or capacitive sensor) disposed (i) along the fluidic plate between two or more conductive tiles of the set of conductive tiles or (ii) inside one of the two or more mixing/testing regions (e.g., a reservoir well), wherein the biosensor electrically terminates either (i) at the set of a corresponding conductive-tile array or (ii) a second set of the conductive-tile array, the self-testing circuit being configured to also assess operative contact of the conductive-tile array associated with the biosensor.
In some embodiments, the system further includes a dielectric material disposed between elements of the set of conductive tiles (e.g., low-strength dielectric fill to planarize the surface and remove the air gap).
In some embodiments, the system further includes a magnetic focusing region for the fluidic plate or the set of conductive tiles, the magnetic focusing region being defined by a field from a magnet (e.g., a traditional magnet, an electromagnetic coil, or a programmable coil array) and a magnetic focusing structure disposed adjacent or in proximity to the magnetic region (e.g., underneath the fluidic plate).
In some embodiments, the magnetic focusing structures comprises a magnetic field guide (e.g., disposed underneath the fluidic plate and configured to redirect magnetic fields from the magnet to a desired location on the fluidic plate or the set of conductive tiles).
In some embodiments, the two or more mixing/testing regions include a sample reservoir, an outlet reservoir, and at least one intermediate reservoir, each disposed adjacent to or along the set of conductive tiles or the interface region of the fluidic plate (e.g., wherein the sample reservoir includes a sample solution).
In some embodiments, the at least one intermediate reservoir comprises a pre-configured buffer solution (e.g., housed in an integrated package assembly) to be introduced into one of the two or more mixing/testing regions.
In some embodiments, the at least one intermediate reservoir comprises a reagent (e.g., housed in an integrated package assembly) to be introduced into one of the two or more mixing/testing regions for mixing with the sample solution.
In some embodiments, the at least one intermediate reservoir comprises an intermediate buffer solution (e.g., Tris Buffer, MES Buffer, PNI Buffer, PE Buffer, or EB Buffer solution).
In some embodiments, the sample reservoir, the outlet reservoir, or the at least one intermediate reservoir is adjacent to the interface region on the fluidic plate.
In some embodiments, the system further includes an electrically-actuated non-mechanically moving valve (e.g., a hydrophobic valve) disposed (i) along the set of conductive tiles or (ii) mixing/testing regions, the electrically-actuated non-mechanically moving valve configured to restrict a fluid flow across the valve in a natural un-actuated state and allow the flow of fluid across the valve when actuated (e.g., wherein one of the first configuration or the second configuration comprises application of an electric potential or current).
In some embodiments, the base system includes: a microcontroller in electrical communication with the cartridge; and a memory (e.g., storing a number of assay protocols selectable by a user) in electrical communication with the microcontroller; and a display interface and/display (e.g., OLED screen) in electrical communication with the microcontroller and configured to display information about the system.
In some embodiments, the intermediate reservoir includes an integrated package assembly disposed on the fluidic plate, the integrated package assembly having (i) a first region to hold a reagent or fluid and (ii) a second region to hold an intermediate storage fluid, the integrated package assembly having a removable or pierceable covering configured, (i) in a non-removed or non-pierced state, to maintain negative pressure at the first region and (ii) in a removed or pierced state to allow the storage fluid to move to the first region while the reagent or fluid move to the second region to contact the fluidic plate.
In some embodiments, the system is configured to perform one of: (i) a DNA isolation protocol with an immobilized filter or (ii) a DNA isolation protocol with magnetic beads.
In another aspect, a method for self-testing a circuit is disclosed, the method comprising: providing a cartridge comprising a microfluidic electrode assembly comprising fluidic plate and a set of conductive tiles disposed along the fluidic plate; inserting the cartridge into a base system (e.g., the base unit of the device, or some other intermediary base system/connection point in the manufacturing process or QA process); assessing operative contact between one of (i) the microfluidic electrode assembly of the cartridge or (ii) the set of conductive tiles and corresponding contact points on the base system; and signaling an error if one or more contact points are disconnected or incompletely connected to the microfluidic electrode assembly cartridge.
In some embodiments, the assessing is performed during run-time of the cartridge.
In some embodiments, the assessing is performed during the manufacturing step of the cartridge.
In some embodiments, the method further includes recycling or reusing a cartridge upon completion of a testing operation.
In another aspect, a cartridge is disclosed, the cartridge configured to couple to a base system, the cartridge comprising: a housing; a microfluidic electrode assembly comprising: a fluidic plate (e.g., microfluidic plate) having two or more mixing/testing regions; a set of conductive tiles disposed along the fluidic plate that connects between the two or more mixing/testing regions, wherein the set of conductive tiles (e.g., pads) terminates at a set of corresponding conductive-tile array located at an interface region on the fluidic plate; a self-testing circuit (e.g., disposed on a separate electronic board or disposed on the fluidic plate) having electronics configured to assess operative contact between (i) the conductive-tile array and (ii) driving circuits configured to actuate the set of conductive tiles to move or mix fluid along the fluidic plate.
The skilled person in the art will understand that the drawings described below are for illustration purposes only.
Each and every feature described herein, and each and every combination of two or more of such features, is included within the scope of the present disclosure, provided that the features included in such a combination are not mutually inconsistent.
The citation and/or discussion of such references is provided merely to clarify the description of the present disclosure and is not an admission that any such reference is “prior art” to any aspects of the present disclosure described herein. In terms of notation, “[n]” corresponds to the nth references in the list. All references cited and discussed in this specification are incorporated herein by reference and to the same extent as if each reference was individually incorporated by reference.
Example System
The instrument controller 104 is operatively connected to the instrument memory 106, the instrument UI output or display 108, and the instrument interface 110. The instrument UI output or display 108, when configured as a display, may include a touchscreen, push buttons, and/or a digital display.
The controller 104 may employ any processing circuitry (for example, but not limited to, an application-specific integrated circuit (ASIC), microcontrollers, microprocessors, complex programmable logic device (CPLD), field-programmable gate array (FPGA), and/or a central processing unit (CPU)). In some examples, the processing circuitry may be electrically coupled one or more sensor arrays, a memory (such as, for example, random access memory (RAM) for storing computer program instructions), and/or a display circuitry.
In some examples, one or more of the procedures may be embodied by computer program instructions, which may be stored by a memory (such as a non-transitory memory) of a system employing an embodiment of the present disclosure and executed by a processing circuitry (such as a processor) of the system. These computer program instructions may direct the system to function in a particular manner, such that the instructions stored in the memory circuitry produce an article of manufacture, the execution of which implements the function specified in the flow diagram step/operation(s). Further, the system may comprise one or more other circuitries. Various circuitries of the system may be electronically coupled between and/or among each other to transmit and/or receive energy, data, and/or information.
In some examples, embodiments may take the form of a computer program product on a non-transitory computer-readable storage medium storing computer-readable program instruction (e.g., computer software). Any suitable computer-readable storage medium may be utilized, including non-transitory hard disks, CD-ROMs, flash memory, optical storage devices, or magnetic storage devices.
Referring still to
In this example, the cartridge controller 124 is operatively coupled to the driver circuitry 128, sensing circuitry 130, and the cartridge interface 126. The connection may be direct or indirect. The cartridge interface 126 is operatively coupled to the instrument interface 110 to facilitate communication between the instrument system 102 and the electronics of the cartridge 120. The sensing circuitry 130 is operatively coupled to the cartridge interface 126 and/or the controller. The built-in-self-tester, or self-testing circuit 160, is operatively coupled to the driver circuitry 128 and/or the cartridge interface 126.
In this example, the cartridge controller 124 and the built-in self-tester 160 are shown implemented in different components. In other embodiments, the built-in-self-tester may be implemented in the cartridge controller 124. Similarly, the cartridge controller 124 may include integrated front-end analog circuitries for sensing or driving output as well as digital communication or memory interface, among others. Examples of sensing and driving circuitries are provided later herein.
Micro fluidic Electrode Assembly. Referring to
In the example shown in
Referring still to
In some implementations, the micro-fluidic electrode assembly 140 includes a plurality of sensors; for example, at least one sensing tile 152 disposed along the fluidic plate 142 adjacent to or integrated with the set of conductive tiles 146. The sensing tile 152 may terminate at the set of corresponding conductive-tile array 148, or a second set of conductive tile array 154. The sensor may be deployed for analysis acquisition or may be deployed to confirm proper operation of the electrowetting or digital microfluidic operations, e.g., in moving fluids within the assembly 140.
In either configuration (for sensing or control), the micro-fluidic electrode assembly 140 may include at least one biosensor (e.g., electrochemical, impedimetric, or capacitive sensor) disposed along the fluidic plate 142 between two or more conductive tiles of the set of conductive tiles 146, or inside one of the two or more reservoir, mixing, and/or testing regions 144. The biosensor may electrically terminate either (i) at the set of corresponding conductive-tile array 148 or (ii) at a second set of conductive-tile array 154. In some implementations, multiple sensing tiles or biosensors are placed on the fluidic plate along the set of conductive tiles and/or within the two or more mixing/testing regions.
Built-in Self Tester. In use, the cartridge 120 is coupled to the instrument system 102. The self-testing circuit 160 includes electronics configured to assess operative contact between the conductive-tile array 148 of the microfluidic electrode assembly 140 and the driving circuits 128 of the cartridge 120. For example, each one of the tiles of the conductive-tile array 148 may contact and communicate with corresponding electric contact points on the cartridge interface 126. Then, each contact point on the cartridge interface 126 may contact and communicate with corresponding contact points of the base interface 110. In the end, each conductive tile 148 and other elements of the microfluidic electrode assembly 140 and of the cartridge 120 as a whole can communicate with the instrument system 102. The self-testing circuit 160 assesses operative contact between these elements to ensure proper communication. In some implementations, the self-testing circuit 160 can be configured to assess operative contact of the conductive-tile array 148 with the sensing tile 152.
In some embodiments, the built-in self-tester 160 is configured to send a test signal into the set of controllable conductive-tiles in an array (e.g., 148) located on the micro-fluidic electrode assembly 140 and sense, for example, the connectivity of the connected load, to verify the proper electrical connection between the driving circuitry 128 and the corresponding control element of the electrowetting tiles. The corresponding conductive-tile array 148 can be a highly dense connector of conductive elements that can be formed on a material different from the connector. The built-in self-tester 160 ensures that the numerous electrical connections required between the micro-fluidic electrode assembly 140 and the corresponding electronics in the cartridge (e.g., 120) is properly established. The built-in self-tester 160 is configured, in some embodiments, to operate during manufacturing operations as part of the quality control process. In addition, the built-in self-tester 160 is configured to be initiated via manual operation as well at the beginning of an analysis operation to ensure that the set of conductive tiles 146 are properly connected to the driving and/or sensing electronics. The built-in self-tester 160 can address manufacturing, assembly, transportation, and storage issues that can have dust in the components, oxidation issues, and/or physical misalignment.
In some embodiments, the built-in self-tester 160 of the cartridge is configured to operate independently without being connected to the instrument system 102. However, when connected to the instrument system 102, the built-in self-tester 160 can also verify the connection with the instrument system 102. In some embodiments, the instrument system 102 may initiate the self-test protocol on the built-in self-tester. In some embodiments, the built-in self-tester 160 is implemented in the instrument system 102.
Reagent/Test Assay. The cartridge can be preloaded with pre-defined assays to operate pre-defined tests in the field. Examples include nucleic acid extraction protocol, tissue sampling or culture growth, and metabolic rate monitoring. In some embodiments, the cartridge include ports to direct assay to specific test chambers to allow for customized operation and testing.
In some embodiments, the cartridge 120 is preloaded with appropriate reagents based on the target assay. The instrument system 102 can provide instructions or other control information to a user via the base user interface 108.
Once coupled together, the cartridge 120 can communicate with the instrument system 102 to also provide its identification type and/or specific control instructions for a given reagent set to be used in the electrowetting or digital microfluidics control operation for the intended or preloaded assay. For example, the cartridge 120 may have a pre-loaded sequence of instructions for a specific test such that the instrument system 102 can perform the required steps of the experiment.
The instrument system 102, including the instrument controller 108, can be configured to run experiments or perform functions in one of a set of selectable configurations, while the cartridge controller 124 may be configured to instruct the instrument system 102 on which configuration to run.
Cartridge Driving Circuitry. The driving circuits 128 are configured to actuate the set of conductive tiles 146 to move or mix fluid along the fluidic plate 142. For example, the driving circuits 128 may actuate the set of conductive tiles 146 such that fluid moves from the two or more reservoir, mixing, and/or testing regions 144 along the set of conductive tiles 146 such that the fluids combine. Then, the fluids can be moved to a sensing tile 152 where measurements can occur (e.g., measurement of target analytes). The signals from the sensing tile 152 or biosensors can be sent to and processed by the instrument system 102 (e.g., the base controller 104).
Example Cartridge Configuration
Housing. As shown in
Magnetic field Field Guide Focusing Assembly. In this example, the cartridge 120 includes a magnetic field focusing assembly. The cartridge base 204 includes an optional integrated magnet 208 that operates with an optional field guide 210. Also disposed between a portion of the housing 122 and the cartridge base 204 are an adapter board 207 and a field guide 210. The integrated magnet 208 and the field guide 210 represent one implementation of the cartridge 120 (see also
Adaptor Board. The adapter board 207 is disposed adjacent to and may be in electrical communication with the microfluidic electrode assembly 140a. The adapter board 207 may carry a variety of circuitry and electronics for the cartridge 120, for example, any one of the cartridge controllers 124, the cartridge interface 126, the driver circuitry 128, and the sensing circuitry 130 as described in relation to
The self-testing circuit 160 (e.g., built-in self-tester) may be disposed on the adapter board 207 or on the microfluidic electrode assembly 140a. The self-testing circuit 160 is configured to assess operative contact between the conductive-tile array 148 and the driving circuit 128. The self-testing circuit 160 is further configured to assess operative contact between the adapter board 207 and one or both of the conductive-tile array 148 of the fluidic plate 142 and the instrument system (e.g., 102).
Microfluidic electrode assembly. As shown in
The fluidic plate 142 of
The microfluidic chip 300a includes a set of conductive tiles 146 (shown as 310), including transport pads 320 and reservoir pads 330 (which can be used as a reservoir storage or for mixing or testing as described herein). The microfluidic chip 300a also includes a set of contact pads 340 (e.g., within the array 154) on either side of the chip configured to contact and communicate with an adjacent circuit board (e.g., adapter board of a cartridge or a base system). Each transport pad 320 and reservoir pad 330 is in electrical communication with a corresponding contact pad 340 via an electrical trace 342. As noted above, the reservoir, testing, and mixing regions can be implemented flexibly and the various regions can be used for more than one purpose.
In the example shown in
The transport pads 320 are configured in this example to be 1 mm by 1 mm with a saw tooth edge design, and the transport pads are configured to move a volume of liquid along the microfluidic chip 300a. For example, a driving circuit (e.g., 128 of
In use, a cartridge (e.g., 120) with the microfluidic chip 300a is coupled to a base instrument system. A testing circuit can assess the operative contact between the contact pads 340 and one or both of the cartridge and the base system. A set of instructions from one of a cartridge or a base system can cause the driver circuits to activate the conductive tiles 310, including the reservoir pads 330 and the transport pads 320. The activation can motivate or urge fluid from the reservoirs to a mixing area 232 to mix with one or more reagent fluids pre-loaded or also brought to the mixing area 322. The fluids can move along with transport pads 320 until the capture area 324 separates a portion of the fluid. A portion of fluid can enter the waste reservoir 338, while a different portion of fluid enters the output reservoir 336 for measurement and analysis.
The process used in example microfluidic chip 300a can match the process used for many nucleic acid extractions kits and accommodate a variety of different DNA extraction kits. The ratios in the microfluidic chip 300a (e.g., electro-wetting on dielectric chip) can match that of the effective ratios of traditional extraction kits, despite the smaller size and volume of sample and reagent. The microfluidic chip 300a (e.g., electro-wetting on dielectric chip) controls the quantity of fluid droplets moved, aided in part by the size of the transport pads 320 being uniform.
In use, the sample DNA and MES buffer are transported from their respective reservoir pads 330 along the transport pads 320 and into the mixing area 322. Magnetic beads are then moved into the mixed fluid at the appropriate ratio, and the mixed fluid is moved, provided, and/or inserted, into the magnetic area 324. The DNA-bound beads precipitate from the surrounding supernatant, and the supernatant containing any unbound DNA is moved to the waste reservoir 338 and discarded. Tris buffer can then be moved through the magnetic are 324 to elute the DNA from the beads while leaving the beads in the magnetic area 324. The eluted DNA can move into the output reservoir 336 for analysis.
Table 1 shows an example reagents for the two protocols of
Electro-Wett Operation with Impedance-Based Feedback
To make a droplet of fluid move reliably, an impedance-based feedback detection circuit 360 can be implemented to monitor the intended droplet movement. An electro-wetting on a dielectric system inherently produces a different impedance based on the presence of the droplet over an active pad (e.g., a transport pad 320 of
As the droplet 350 reaches the active pad, it displaces the media, removing Cmedia and inserting a low resistive path formed by the conductive droplet (Rdrop). The low resistance of the droplet 350 causes a larger voltage drop across Rtune. Because the capacitance of Cmedia is dependent on the geometry of the EWOD chip (pad size, ground plane height, etc.) Rtune is selected to produce a max voltage that is within the range of the sensing Analog to Digital Converter (ADC) of the system. The signal seen at VFB is an attenuated version of the activation signal with a 0 V direct current (DC) offset due to the insulating layer of the EWOD chip (Cins) forming a high pass filter. Therefore, VFB is sent through a half wave rectifier and low pass filter to create a DV voltage (Vsense) that is proportional to the droplet (350) position.
The controller (e.g., 124), e.g., a microcontroller can monitor Vsense to determine if the droplet 350 has reached the intended destination and is able to progress to the next sequence in the protocol. The feedback system can detect whether a droplet 350 fails to move on to the active pad. If so, the applied voltage for the movement is adjusted, and the movement is tried again until the droplet 350 moves onto the active pad or the maximum number of trials have been reached. Common situations for a droplet 350 failing to be moved onto an active pad include dirt particles in the EWOD system, manufacturing variations resulting in surface imperfections, and dielectric breakdown during operation.
Example Integrated Magnet with Fieldguide
As discussed above in relation to
Some assays, such as DNA isolation, include the use of magnetic beads. Magnet 472 (e.g., a traditional magnet, electromagnetic coil, or programmable coil array) creates a magnetic field used to keep the beads stationary during a portion of the assay. Due to the small size of the microfluidic electrode assembly 400b, 400c, the magnetic field can affect the beads throughout the chip, causing unwanted movement. The magnetic field guide 470 redirects stray magnetic fields and leaves a focused field in a desired location 474.
The microfluid electrode assembly (e.g., 140, 400a, 400b) can be formed over a cartridge base 204, e.g., formed of a plastic (e.g., thermoplastic). The cartridge base 204 includes a magnet 208 that generates a magnetic field (shown by field lines 449 and stray field lines 451) over the conductive-tile array 146. The magnets provide a static field 449, 451 over the conductive-tile array 146 that can then generate dynamic fields to urge movement or retention of the droplet at desired locations in the channels of the microfluidic electrode assembly. The magnets reduce the operational electrical requirements of the conductive-tile array 146 and the associated driving circuitries. While a permanent magnet 208 is shown in the example of
As shown in microfluidic electrode assemblies 400a, the stray magnetic fields (shown by lines 451) are outside of the desired area and are known to cause unwanted movement or unwanted loss.
In microfluidic electrode assemblies 400b, by focusing the magnetic field with a magnetic field guide 470, the stray magnetic fields can be redirected into a narrower beam to provide a focused field for a desired location 474. As shown in
Conductive-Tile Array with Dielectric In-Fill
Existing manufacturing techniques for digital microfluidic devices can leave the airgap between the electrode pads. It is observed that when coating the surface the dielectric materials, this can airgap presents a reliability problem for devices operating at high voltage when moving droplets.
In
As shown in
Example Electronic Circuitry
Driver Circuit.
Built-in Self-Test Circuit.
Example Reagent Storage and Packaging
The cartridge (e.g., 120) may be configured with a passive reagent storage and packaging that maintains the pre-loaded reagents in an isolated inert chamber or location that is not in contact with the testing circuitries or microfluidic circuits. Prolonged contact, and even exposure, of the reagents to the electronic or fluidic circuit while in storage can degrade the operation and/or performance of the cartridge after a period of storage. To reduce the number of active components and thus the cost of the cartridge, the pre-loaded reagents may be maintained in the chamber that is isolated from the electronic or fluidic circuit by a buffer solution (e.g., a silicon oil).
The first layer 604 of the packaging isolation structure 601, as a buffer layer, is in direct contact with the microfluidic assembly (e.g., 140b) and includes a buffer solution or oil in a buffering chamber 608 formed in the layer. The second layer 606 of the packaging isolation structure 601, as a reagent storage layer, is in direct contact with the first layer (e.g., 140b) and includes the regent storage chamber 610 that houses the pre-loaded reagents or various solutions to be employed in the analysis of the cartridge. The buffer solution or oil is a low-density fluid and has a density that is lower than that of the reagents or various solutions. With the cover seal 612 placed over in sealed contact with the packaging isolation structure 601, as shown in diagram 600a, a vacuum or lower pressure is formed within reagent storage chamber 610 of the reagent storage layer 606. With the cover seal 612 being removed or punctured, as shown in diagram 600b, the vacuum or lower pressure environment is thus removed as the interior structures are open to the atmosphere, and hydrostatic pressure dynamics between the buffer solution or oil in the chamber 608 and the reagent storage chamber 610 are initiated in which the low/lower density buffer solution or oil in the buffer chamber 608 is allowed to flow from the buffer chamber 608 to the reagent storage chamber 610 while the pre-loaded reagent or solution of each reagent storage chamber 610 is allowed to flow into the buffer chamber 608 that is contact with the microfluidic assembly (e.g., 140b). To this end, as shown in diagram 600b, the reagent is in contact with a portion of the microfluidic assembly (e.g., 140b) and is now ready for electrowetting operation as described herein.
Diagram 600c shows an example configuration of the cartridge having the two intermediate storage layers 604, 606, that form chambers 608, 610. Diagram 600d shows an above-view overlap between the different structures of the layers. As shown in diagrams 600c and 600d, the reagent storage chamber 610 is seated above the buffer chamber 608. The buffer chamber 608 is connected over a channel 614 to analyte/reagent holding chamber 620 (e.g., reservoir 144c) that overlaps with the tiles of the conductive-tile array 146. The buffer chamber 608, and maybe the channel 614, is pre-loaded with the silicon oil 622 to fluidically isolate the content of each reagent tank 610 from other areas of the microfluidic chip 600. The isolation also reduces risk of premature mixing or fluid flow before the desired operation.
Similar operations can be performed for the sample. Diagram 600e shows the passive storage structure 601 being filled with trapped air or inert gas in a corresponding structure to the reagent storage chamber 610 (shown as chamber 610′). As shown in diagram 600f, the seal cover is removed during operation and the sample can be placed in the chamber 610′, which, as shown in diagram 600g, the sample is allowed to flow into the reservoir 608.
Referring to
The second layer 606, as a reagent storage layer, of the packaging isolation structure 601 provides the reagent tank layer where specific reagents are stored for a given assay. While not shown, the round plane layer can be fabricated between the first and second layers 604, 606. The cover seal 612 is a cover layer that seals the reagent in the reagent tanks. When pulled open, it allows reagents to flow to the desired reservoirs for intended applications. In
Example Hydrophobic Valve Function and Method of Construction
As discussed above, reservoirs (e.g., 144c and 144d) may be connected to other structures in the microfluidic device via an electronic valve 214. The electronic valve 214 is non-mechanical (e.g., a hydrophobic valve) and is configured to restrict a fluid flow across the valve 214 in a natural un-actuated state. The valve 214 is configured to allow fluid flow across the valve 214 when actuated (e.g., wherein one of the first configuration or the second configuration comprises the application of an electric potential or current).
For actuation, the electronic valve 214 may be a hydrophobicity effect-based micro-valves that use the principle of capillary action and direct electrowetting. Capillary action causes movement until the fluid reaches the valve area. The bottom of the valve area can be made of metal or a self-assembled monolayer (SAM). In the valve region, movement through it can be controlled by electrowetting of the bottom electrode area. Fluid can then move in a microchannel due to the hydrophilic nature of the glass-bottom till it stops at the hydrophobic valve area made of the gold electrode. The flow can start again after the application of a potential between fluid and metal electrode. The valve width can be configured to be adjusted to stop the fluid. The flow velocity depends on the geometry and wettability of the flow channels. It is defined by the Washburn equation, as Equation 1 below:
In Equation 1, v=average flow velocity, h=height of the flow channel, w=width of the flow channe η=viscosity of the solution, x=distance between the inlet of the flow channel to the meniscus of the moving liquid column, γLV=interfacial tension between the solution and the capillary wall, θPDMS=contact angles on PDMS, θGlass=contact angles on glass.
Based on Equation 1, the geometry of the experimental valve can be designed. In a study, experiments were conducted for nine models of valves with widths of 80 micrometers, 100 micrometers, and 120 micrometers with three heights of 40 micrometers, 60 micrometer, and 80 micrometer. The width of the microchannel was kept constant at 300 micrometers for all. However, in other implementations, various other geometries are available.
Construction of Hydrophobicity-Effect-Based Micro-Valve.
The glass of the glass substrate 720 at the bottom of microchannel 716 connecting microvalve 714 is hydrophilic. Gold electrodes 722 are hydrophilic immediately after cleaning, but on exposure to air, a hydrophobic monolayer of carbonaceous contamination is formed on the surface. This layer is used as a valve. The contact angle on the gold is changed by performing a plasma treatment. The PDMS is hydrophobic with a contact angle 110°. No change in contact angle is done for PDMS. If PDMS is treated, then valve action is not seen, and fluid flows from one end to another with a minimal plasma treatment duration.
Construction of Hydrophobicity-Based Microvalve.
Phase 1 of Model Fabrication—Microvalve SU8 Mold.
Table 4 shows an example process to generate the microvalve SU8 model.
Phase 1B of Model Fabrication—Acrylic mold for valve.
The acrylic mold is formed of an Acrylic sheet (thickness 5.4 mm), Superglue (Superglue corporation) using a Laser engraver (LS-1416, BOSS Laser, FL, USA). The design was created using AutoCAD Inventor 2019. It is then converted to “dxf” file format and then to “rld” file format, which is readable by BOSS laser writer.
Phase 2—Procedure for Creation of Electrodes. Following the fabrication of the valve mold, gold electrodes can be fabricated on the valve mold.
Table 5 shows an example process to create the electrode.
Phase 3—Procedure for Preparation of Valve in PDMS.
Procedure for Creation of Valve Assembled on Electrodes. The procedure for the creation of a valve assembled on electrodes utilizes a plasma asher and includes the following steps shown in Table 7.
Testing the Valve. Tests were performed to verify the structure and function of the constructed valve. KCl (1M) was prepared by dissolving the required quantity of KCl in DI water. Phosphate Buffer Solution (PBS), Gmop, Foetal Buffer Solution (FBS), and Cell culture solution were procured. Each of these was dyed using 10 drops of food color.
Experiments conducted revealed various properties that would enhance the valve's function, including the plasma treatment duration time needed to achieve valve action, retention probability for each width, the voltage at which the valve would operate, and the corresponding valve width.
Table 8A shows a method to find the plasma treatment duration needs to achieve valve action.
Table 8B shows a method to find the retention probability for each width.
Table 8C shows a method to find the voltage at which the valve worked and the corresponding valve width.
At step 801, one volume of sample was moved to the mixing area. At step 802, the magnetic beads were moved to the mixing area and (at step 803) mixed with the sample. Finally, at step 804, the full volume of the mixture was moved over the magnet in the capture area. After letting the beads settle over the magnet, at step 805, excess liquid was moved to the waste reservoir, leaving bound DNA over the magnet. Finally, the elution buffer was moved through the capture area into the output reservoir (step 805).
The programs stored in memory can be managed through custom software on a PC and downloaded to the device via a Universal Serial Bus (USB) port. Another microcontroller is incorporated into the system to translate the USB packets and store them into the EEPROM. Additionally, an integrated on-board power supply capable of output voltage up to 200 V is incorporated into the system to offer the capability of moving a wider range of liquid types. Finally, to maximize portability, the entire system is powered from an integrated lithium ion battery which provides up to 80 h of active run time and over 300 h in standby. The battery can be recharged via a USB port.
To keep the firmware of the main controller light, the PC software populates the EEPROM with a specific format such that the protocols can be called back easily by the microcontroller. When the device is first powered on, a splash screen is displayed while the microcontroller sets up its peripherals. Once ready, the Protocol Select menu is displayed, where the user can navigate to the desired protocol. During the execution of the selected protocol, the display shows protocol progress. Additionally, the user can stop the active protocol through the keypad, where the user is prompted to confirm the request. If the request to cancel the protocol is confirmed, the user is taken back to the Protocol Select menu.
Although example embodiments of the present disclosure are explained in some instances in detail herein, it is to be understood that other embodiments are contemplated. Accordingly, it is not intended that the present disclosure be limited in its scope to the details of construction and arrangement of components set forth in the following description or illustrated in the drawings. The present disclosure is capable of other embodiments and of being practiced or carried out in various ways.
It must also be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” or “5 approximately” one particular value and/or to “about” or “approximately” another particular value. When such a range is expressed, other exemplary embodiments include the one particular value and/or to the other particular value.
By “comprising” or “containing” or “including” is meant that at least the name compound, element, particle, or method step is present in the composition or article or method, but does not exclude the presence of other compounds, materials, particles, method steps, even if the other such compounds, material, particles, method steps have the same function as what is named.
In describing example embodiments, terminology will be resorted to for the sake of clarity. It is intended that each term contemplates its broadest meaning as understood by those skilled in the art and includes all technical equivalents that operate in a similar manner to accomplish a similar purpose. It is also to be understood that the mention of one or more steps of a method does not preclude the presence of additional method steps or intervening method steps between those steps expressly identified. Steps of a method may be performed in a different order than those described herein without departing from the scope of the present disclosure. Similarly, it is also to be understood that the mention of one or more components in a device or system does not preclude the presence of additional components or intervening components between those components expressly identified.
The term “about,” as used herein, means approximately, in the region of, roughly, or around. When the term “about” is used in conjunction with a numerical range, it modifies that range by extending the boundaries above and below the numerical values set forth. In general, the term “about” is used herein to modify a numerical value above and below the stated value by a variance of 10%. In one aspect, the term “about” means plus or minus 10% of the numerical value of the number with which it is being used. Therefore, about 50% means in the range of 45%-55%. Numerical ranges recited herein by endpoints include all numbers and fractions subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.90, 4, 4.24, and 5).
Similarly, numerical ranges recited herein by endpoints include subranges subsumed within that range (e.g., 1 to 5 includes 1-1.5, 1.5-2, 2-2.75, 2.75-3, 3-3.90, 3.90-4, 4-4.24, 4.24-5, 2-5, 3-5, 1-4, and 2-4). It is also to be understood that all numbers and fractions thereof are presumed to be modified by the term “about.”
This application claims priority to, and the benefit of, U.S. Provisional Patent Application No. 63/321,464, filed Mar. 18, 2022, entitled “PORTABLE AND BATTERY-OPERATED DIGITAL MICROFLUIDICS DEVICE,” which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63321464 | Mar 2022 | US |
