BACKGROUND

[0001 ] Digital microfluidic systems may be programmed using the language of traditional biological protocols to perform a variety of chemical, biological, and biochemical processes, such as nucleic acid testing. Delivery of reagents to a process site may be accomplished by digitization of the reagents and processing them as packets so that the reagent volume is small, enabling a large number of experiments with low reagent cost, and a compact design. Such digital microfluidic systems are often purpose built for specific assays.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] FIGS. 1 A - 1 D are schematic diagrams of an example device that uses a dynamically configurable operation space to transport, merge and split fluid droplets.

[0003] FIG. 2 is a flowchart of an example method that uses the example device.

[0004] FIGS. 3A - 3D are schematic diagrams of an example device that uses a dynamically configurable operation space to transport multiple fluid droplets over linear and staggered buses.

[0005] FIGS. 4A - 4F are schematic diagrams of an example device that uses a dynamically configurable operation space to synchronously and asynchronously transport multiple fluid droplets over linear and staggered buses. [0006] FIGS. 5A - 50 are schematic diagrams of an example device that uses a dynamically configurable operation space to transport multiple fluid droplets over intersecting buses.

[0007] FIGS. 6A and 6B are schematic diagrams of an example device that uses a dynamically configurable operation space to transport multiple fluid droplets of different sizes.

[0008] FIGS. 7A - 71 are schematic diagrams showing stages of operating an example device for performing biological operations.

DETAILED DESCRIPTION

[0009] Dispensing of reagents to a target medium may include using a digital microfluidic (DMF) device having a plurality of electrode platforms configured to hold a fluid droplet and further transport the fluid droplet to an adjacent platform. The platforms may include a sample reservoir, buffer reservoir and a waste reservoir and these reservoirs may act as a storage space and hold droplets that are produced in mixing and are needed again in a subsequent mixing step. A sequence of voltages may be applied to an array of such platforms that cause the droplets to move from one platform to another platform along a sample pathway. Some DMF devices have a small number of electrodes for transporting only a few droplets at a time from one region of the device to another, while other DMF devices have static single lane buses to transport droplets from one region to another, which results in slow droplet transport since the number of droplets being transported is low.

[0010] To transport a large number of droplets a device is provided having an array of electrodes for transporting droplets of fluids along dynamically reconfigurable pathways (also referred to as buses). A sequence of voltages can be applied to the electrodes for causing the droplets to move from one electrode to another, as well as to split/merge droplets for dynamic control of volume and speed of the fluid being transported. The effective size of the pathways can be dynamically changed for bandwidth optimization and the droplets can be transported using sequential or simultaneous and synchronous transport.

[0011 ] In the examples, a method comprises selectively energizing a first electrode of an array of electrodes for moving a first fluid droplet toward the first electrode; selectively energizing a second electrode of the array of electrodes for moving a second fluid droplet toward the second electrode; and selectively de-energizing further electrodes of the array of electrodes surrounding the first fluid droplet and second fluid droplet for maintaining separation between the first fluid droplet and second fluid droplet or selectively energizing further electrodes for merging the first fluid droplet and second fluid droplet.

[0012] The further electrodes can be energized sequentially to sequentially move the first fluid droplet and second fluid droplet.

[0013] The further electrodes can be energized simultaneously to simultaneously move the first fluid droplet and second fluid droplet.

[0014] The first fluid droplet and second fluid droplet can be disposed on a row or column of the array forming a first linear bus and be spaced apart by one electrode.

[0015] The first fluid droplet and second fluid droplet can be diagonally adjacent forming a staggered bus and be disposed on adjacent rows or columns of the array.

[0016] The first fluid droplet and second fluid droplet can be disposed on a row or column of the array forming a first linear bus and be spaced apart by two electrodes.

[0017] The first fluid droplet and second fluid droplet can be disposed on adjacent rows or columns of the array forming a staggered bus and not be diagonally adjacent.

[0018] The further electrodes can be selectively energized to split the first fluid droplet into two fluid droplets. [0019] Further electrodes of the array of electrodes surrounding a third fluid droplet and a fourth fluid droplet can be selectively energized, wherein the third fluid droplet and fourth fluid droplet are disposed on a row or column of the array forming a second linear bus perpendicular to the row or column of the array on which the first and second fluid droplets are disposed, and can be spaced apart by more than two electrodes, and the further electrodes can be energized simultaneously to simultaneously move the third fluid droplet and fourth fluid droplet at a slower rate than the first and second fluid droplets to prevent droplet collision where the first linear bus and second linear bus intersect.

[0020] In other examples, a device comprises an array of electrodes for transporting droplets of fluids along dynamically configurable routes, the array having a first electrode that is selectively energized for moving a first fluid droplet toward the first electrode; a second electrode that is selectively energized for moving a second fluid droplet toward the second electrode; and further electrodes surrounding the first fluid droplet and second fluid droplet that can be selectively de-energized for maintaining separation between the first fluid droplet and second fluid droplet or selectively energized for merging the first fluid droplet and second fluid droplet.

[0021 ] In further examples, a device comprises a first short-term fluid storage memory; a second short-term fluid storage memory; and a dynamically configurable operation space having an array of electrodes for transporting droplets of fluids along dynamically configurable routes and performing an operation on the droplets of fluids received from the first short-term fluid storage memory and second short-term fluid storage memory and outputting the result of the operation to one of the first short-term fluid storage memory or second short-term fluid storage memory, and for performing a subsequent operation on droplets of fluids from the one of the first short-term fluid storage memory or second short-term fluid storage memory and the other short-term fluid storage memory and outputting the result of the subsequent operation to the other shortterm fluid storage memory, and wherein the array includes a first electrode that is selectively energized for moving a first fluid droplet toward the first electrode; a second electrode that is selectively energized for moving a second fluid droplet toward the second electrode; and further electrodes surrounding the first fluid droplet and second fluid droplet that are selectively de-energized for maintaining separation between the first fluid droplet and second fluid droplet or selectively energized for merging the first fluid droplet and second fluid droplet..

[0022] FIG. 1 A shows a device 100 having an array 110 of electrodes (1 ,1 ) ... (9,13) arranged in rows and columns for transporting droplets of fluids along dynamically configurable routes. In operation, energizing an electrode results in an electrostatic force that causes a fluid droplet to move to the electrode whereas grounding the electrode permits the fluid droplet to be moved away from it.

[0023] Fig. 2 is a flowchart of an example method for transporting droplets of fluids via the electrodes of the array 1 10, starting at block 200. At block 210, a first electrode (4,6) is selectively energized for moving a first fluid droplet 114 toward the first electrode. At block 220, a second electrode (4,8) is selectively energized for moving a second fluid droplet 118 toward the second electrode, as shown in FIG. 1 B.

[0024] To maintain separation between the first fluid droplet 114 and second fluid droplet 1 18 at block 225, further electrodes (3,6), (4,5), (5,6) and (4,7) surrounding the first fluid droplet 114 are selectively de-energized (grounded) and further electrodes (3,8), (4,9), (5,8) and (4,7) surrounding the second fluid droplet 118 are selectively de-energized (grounded) at block 230, for preventing the two fluid droplets from occupying adjacent electrodes.

[0025] When two fluid droplets occupy adjacent electrodes, merging of the droplets occurs. Therefore, to merge the first fluid droplet 114 and second fluid droplet 118 at block 225, further electrodes (4,6), (4,7) and (4,8) are energized at block 240 for merging the droplets 114 and 118 into a merged droplet 120 of twice the size, as shown in FIG. 1 C. Then, to reshape the fluid droplet 120 so that it occupies a single energized electrode (4,6), electrodes (4,8) and (4,7) can be de-energized as well as electrodes (3,5), (3,6), (3,7), (4,5), (5,5), (5,6), (5,7) and (4,7) resulting in the large circular fluid droplet 120 as shown in FIG. 1 D.

[0026] The operations depicted in FIGS. 1 B - 1 D can be reversed for splitting the large fluid droplet 120 shown in FIGS. 1 C and 1 D into two fluid droplets 1 14 and 1 18 by energizing electrode (4,8) at block 230, and deenergizing electrode (4,7). The method ends at block 250.

[0027] One advantage of merging fluid droplets, as depicted in FIG. 1 D, is that larger quantities of fluid can be transported at a greater rate than when the droplets are separated, as shown for example in FIG. 1 B Bearing in mind that two fluid droplets will merge if they occupy adjacent electrodes, fluid droplets may be transported either sequentially or simultaneously depending on the spacing between the droplets. Also, fluid droplets can be transported sequentially or simultaneously via either a linear bus configuration or a staggered bus configuration.

[0028] As shown in FIG. 3A, when transporting fluid droplets 1 14 and 1 18 sequentially across the array 110, fluid droplet 114 must move before fluid droplet 118 to avoid the droplets occupying adjacent electrodes. Therefore, electrode (4,9) is energized and then electrode (4,7) is energized for sequential transport along a linear bus (i.e. a 1 -bit wide bus comprising the line of electrodes (4,1 ) ... (4,13)).

[0029] As shown in FIG. 3B, fluid droplet 1 14 must move before fluid droplet 118 also for sequential transport along a staggered bus (i.e. the 2-bit wide bus comprising lines of electrodes (3,1 ) ...(3,13) and (4,1 )...(4, 13)).

[0030] As shown in FIG. 3C, when transporting fluid droplets 114 and 1 18 simultaneously across the array 110, fluid droplets 114 and 1 18 must be spaced apart by two electrodes to avoid the droplets occupying adjacent electrodes when simultaneously energizing electrodes (4,10) and electrode (4,7) for simultaneous transport along the linear bus. [0031 ] As shown in FIG. 3D, fluid droplets 114 and 118 must be spaced apart by one column of electrodes (i.e. not diagonally adjacent) for simultaneous transport along a staggered bus.

[0032] As shown in FIG. 4A, when transporting multiple fluid droplets 114, 118, 122 and 124 sequentially along a linear bus, fluid droplet 114 must move before fluid droplet 118, fluid droplet 118 must move before fluid droplet 122 and fluid droplet 122 must move before fluid droplet 124, to avoid any droplets occupying adjacent electrodes. Therefore, electrode (4,10) is energized, followed by electrode (4,8), then electrode (4,6) and finally electrode (4,4), and the electrode energizing sequence is repeated for sequential transport of fluid droplets 1 14, 118, 122 and 124 along the linear bus.

[0033] Similarly, as shown in FIG. 4B, when transporting multiple fluid droplets 1 14, 118, 122 and 124 sequentially along a staggered bus, fluid droplet 114 must move before fluid droplet 118, fluid droplet 118 must move before fluid droplet 122 and fluid droplet 122 must move before fluid droplet 124, to avoid any droplets occupying adjacent electrodes. Therefore, electrode (3,9) is energized, followed by electrode (4,8), then electrode (3,7) and finally electrode (4,6), and the electrode energizing sequence is repeated for sequential transport of fluid droplets 114, 118, 122 and 124 along the staggered bus.

[0034] As shown in FIG. 4G, multiple fluid droplets 114, 118, 122, 124, 126, 128, 130 and 132 can be arranged on a 2-bit wide staggered bus, and can be moved either asynchronously as discussed with reference to FIG. 4B, or synchronously wherein fluid droplets 114 and 126 move together by synchronous energizing of electrodes (4,10) and (5,9), followed by fluid droplets 118 and 128, then fluid droplets 122 and 130 and then fluid droplets 124 and 132.

[0035] As shown in FIG. 4D, multiple fluid droplets 114, 118, 122, 124, 126, 128, 130 and 132 can be arranged on a 4-bit wide staggered bus, and can be moved either asynchronously, or synchronously wherein fluid droplets 114 and 126 move together by synchronous energizing of electrodes (3,9) and (5,9), followed by fluid droplets 1 18 and 128, then fluid droplets 122 and 130 and then fluid droplets 124 and 132.

[0036] In FIG. 4E, multiple fluid droplets 114, 118, 122, 124, 126, 128, 130 and 132 can be arranged on two 2-bit wide linear buses, and can be transported sequentially and synchronously by moving fluid droplet 114 by energizing electrode (4,10), followed by fluid droplets 126 and 118, then fluid droplets 128 and 122, and then fluid droplets 130 and 124 and then finally fluid droplet 132.

[0037] In FIG. 4F, multiple fluid droplets 114, 118, 122, 124, 126, 128, 130 and 132 can be arranged on two side-by-side 1 -bit wide linear buses with bus isolation, and can be transported sequentially and asynchronously by moving fluid droplet 114, followed by fluid droplets 118 and 128, then fluid droplets 122 and 128, then fluid droplets 130 and 124 and then finally fluid droplet 132.

[0038] FIGS 4A - 4F show several examples of linear and staggered buses of various widths, where fluid droplets can be sequentially or simultaneously transported either synchronously or asynchronously. Other configurations of linear and staggered buses of various widths are possible, provided fluid droplets are transported so as not to occupy adjacent electrodes.

[0039] FIGS. 5A - 5C show an example of fluid droplet transport over two orthogonal high-speed busses operating at different droplet transport rates to avoid droplet collision at the intersection between the busses. Fluid droplets 1 14 and 1 18 are transported along a 1 -bit wide linear bus comprising electrodes (4,1 ) ... (4,5), while fluid droplets 122 and 124 are transported along an orthogonal 1 -bit wide linear bus comprising electrodes (7,3) ... (1 ,3), where the intersection between buses is at electrode (4,3).

[0040] In order to avoid droplet collision at the bus intersection, the transport rate on the bus comprising bus electrodes (7,3) ... (1 ,3) is reduced relative to the rate on the bus comprising electrodes (4,1 ) ... (4,5).

[0041 ] For high volume droplet transport, droplets can be merged as discussed with reference to FIGS. 1 C - 1 D. Thus, as shown in the example of FIG. 6A, multiple fluid droplets 114, 118, 122, 124, 126, 128, 130 and 132 can be transported along a 4-bit wide bus, while the same volume of fluid in merged droplets 120 and 134 can be transported along the same bus, as shown in FIG. 6B. In general, a bus can be sized to handle N bits of a packet size A, or M bits of a packet size B, where packet size B is greater than A and the number of bits transported is reduced. For example, in FIG. 6A the bus size is N=4 for transporting eight droplets of size A, while in FIG. 6B, N=2 and B=4*A.

[0042] As discussed above, sequential fluid droplet transport results in a higher volume over a smaller bus size but lower transport speed than simultaneous fluid droplet transport. Merging and splitting of droplets results in improved bus utilization, and bus crossing of fluid droplets can be achieved using prioritization and bus bandwidth modulation.

[0043] These aspects can be used in a digital microfluidic device for transporting digital microfluidic droplets in a flexible (reprogrammable manner). Transporting of droplets from one region of an operation space of digital microfluidic device to another region permits different operations to be performed on the fluid droplets. For example, one region may be responsible for storing reagents and another region for pulling magnetic beads out of droplets, while another region may be responsible for heating the droplets. It desirable to transport a large number of droplets from one region to another especially when dealing with large sample volumes compared to droplet volume. It is also desirable to transport the droplets from region to region quickly as this reduces the time of the overall assay. It is desirable to also change the locations of the regions programmatically as it allows for a more flexible cartridge and therefore support a larger number of assays without the need to change hardware. Thus, it is desirable to change the bus routing programmatically as well.

[0044] FIGS. 7A - 7I show an example digital microfluidics device 700 employing the techniques of fluid droplet transport set forth herein for performing a variety of chemical, biological, and biochemical processes, such as nucleic acid testing. FIG. 7A shows the example device 700 in perspective and FIG. 7B is a plan view thereof. FIG. 70 is s schematic illustration of the device 700. FIGS. 7D - 7I schematically illustrate stages of a biological operation using the device 700.

[0045] In FIG. 7C, the device 700 includes a first short-term fluid storage memory including a plurality of sub-memories 701 a, 701 b, 701 c and 701 d arranged in a stack and hash table format. A second short-term fluid storage memory likewise includes a plurality of sub-memories 701 'a, 701 'b, 701 'c and 701 ’d arranged in a stack and hash table format.

[0046] First long-term fluid storage memories can include a plurality of submemories 701 ”a - 701 ”h, arranged in a stack and hash table format, and second long-term fluid storage memories likewise can include a plurality of submemories 701 ”’a - 701 ”’h arranged in a stack and hash table format.

[0047] In an example biological process, a biological sample 710 can be loaded into long-term sub-memory 701 ”a (e.g. a 1 ml sample of a virus such as Influenza H1 N1 , or a bacterium such as Chlamydia or Mycoplasma, introduced via a room-temperature Universal Transport Mechanism (UTM)), as shown in FIG. 7D. Similarly, a composition of magnetic beads 712 can be loaded into long-term sub-memory 701 ”c, a wash buffer 714 can be loaded into long-term sub-memory 701 ”d and an elution buffer 718 can be loaded into long-term submemory 701 ”g. Long-term sub-memory 701 ”e is reserved for the master mix, which is a mixture that contains dNTPs (monomers for building DNA strands), magnesium chloride, polymerase enzyme (enzyme required for building DNA stands) a buffering agent (such as phosphate) to maintain pH and may also include a dye to indicate the amount of DNA polymer produced and primers for a PCR reaction.

[0048] In FIG. 7E, a portion 720 of the biological sample 710 is loaded from sub-memory 701 'a into sub-memory 701 b, and a portion 722 of the composition of magnetic beads 712 is loaded from sub-memory 701 'c into sub-memory 701 c [0049] In FIG. 7F, the droplets of portion 720 of the biological sample 710 and droplets of the portion 722 of the composition of magnetic beads 712 are mixed (for example at a ratio of 10:1 ) in a heat processing region 724 for the dynamically configurable operation space 106. The resultant mixture 726 of sample and magnetic beads is loaded as a merged fluid droplet into short-term sub-memories 701 ’b and 701 ’c for cooling to room temperature.

[0050] In Fig. 7G, a portion 728 of the wash buffer 714 is loaded into shortterm sub-memory 701 ’d, and a portion 730 of the elution buffer 718 is loaded into short-term sub-memory 701 'a. Droplets 732 of the mixture 726 are transported from sub-memories 701 ’b and 701 ’c to a magnetic region 734 of the dynamically configurable operation space 106. The magnetic beads are pulled down at 736 by magnetic force in the magnetic region 734 and washed at 738 with droplets 740 of wash buffer 728, resulting in droplets 742 of magnetic beads and wash. The droplets 742 are eluted at 744 with droplets 746 of the elution buffer 718, yielding droplets 748 of eluted DNA 750, which are transported for bulk storage in sub-memory 701 b. Following elution, the remaining droplets 752 are washed at 754 and transported along with droplets 756 of supernatant from the sample and droplets 758 of supernatant from the wash to waste storage 760 in sub-memory 701 ”’a.

[0051 ] In FIG. 7D, the fluid droplets 732, 740, 742, 746, 748, 752, 756 and 758 are transported over linear and staggered busses, a number of which intersect (for example fluid droplets 748 crossing the linear bus transporting fluid droplets 756, 758, and 752), using the droplet transport principles discussed herein.

[0052] In Fig. 7H, a portion 762 of the master mix 716 is loaded into shortterm sub-memory 701c. Droplets 764 of eluted DNA 750 are mixed with droplets 766 of master mix 762 in the dynamically configurable operation space 106, and the resulting merged droplets 768 of eluted DNA and master mix are transported for bulk storage 770 in sub-memory 701 ”’h. The operations depicted in FIGS. 7E to 7H are repeated until all of the sample 710 has been processed. [0053] In FIG. 7I, a portion 772 of the eluted DNA and master mix 770 is loaded into short-term sub-memory 701 'a. Droplets 774 of the eluted DNA and master mix are cycled through heated regions 724 and 776 while fluorescence from the droplets 774 is detected via real-time PGR for identifying specific, amplified DNA fragments.

[0054] The device 100 is simple to control and allows user access to a large set of biological protocols. Operation of the device 100 is scalable to many assays without the need for multiple concatenated platforms.

[0055] It should be apparent from the above that complexity of microfluidic structures, such as a nucleic acid testing device, may be reduced by using device 100 or a plurality of such be linked to form a system of nodes. The complexity of nucleic acid testing, such as microfluidics for mixing a sample with several reagents as well as filtration, separation, heating, washing and other unit process steps, is reduced.

[0056] It should be recognized that features and aspects of the various examples provided above can be combined into further examples that also fall within the scope of the present disclosure. In addition, the figures are not to scale and may have size and shape exaggerated for illustrative purposes.