Droplet manipulation device

• US 10,022,719 B2
• Filed: 11/09/2015
• Issued: 07/17/2018
• Est. Priority Date: 09/24/2002
• Status: Active Grant

• Current Assignee: Duke University
• Original Assignee: Duke University
• Inventors: Pollack, Michael G., Pamula, Vamsee K., Fair, Richard B.
• Primary Examiner(s): NOGUEROLA, ALEXANDER STEPHAN
• Application Number:
  US14/935,823
• Publication Number:
  US 20160114320A1
• Time in Patent Office: 981 Days
• CPC Class Codes: B01F 31/65 the materials to be mixed being directly submitted to a pulsating movement, e.g. by means of an oscillating piston or air column
• CPC Class Codes: B01F 33/3021 the components to be mixed being combined in a single independent droplet, e.g. these droplets being divided by a non-miscible fluid or consisting of independent droplets
• CPC Class Codes: B01F 33/3031 using electro-hydrodynamic [EHD] or electro-kinetic [EKI] phenomena to mix or move the fluids
• CPC Class Codes: B01F 33/30351 using hydrophilic/hydrophobic surfaces
• CPC Class Codes: B01L 2200/06 Fluid handling related problems
• CPC Class Codes: B01L 2200/0605 Metering of fluids
• CPC Class Codes: B01L 2200/10 Integrating sample preparation and analysis in single entity, e.g. lab-on-a-chip concept
• CPC Class Codes: B01L 2300/089 Virtual walls for guiding liquids
• CPC Class Codes: B01L 2300/161 Control and use of surface tension forces, e.g. hydrophobic, hydrophilic
• CPC Class Codes: B01L 2300/165 Specific details about hydrophobic, oleophobic surfaces
• CPC Class Codes: B01L 2400/0415 electrical forces, e.g. electrokinetic
• CPC Class Codes: B01L 2400/0427 Electrowetting
• CPC Class Codes: B01L 3/00 Containers or dishes for laboratory use, e.g. laboratory glassware; Droppers
• CPC Class Codes: B01L 3/5027 by integrated microfluidic structures, i.e. dimensions of channels and chambers are such that surface tension forces are important, e.g. lab-on-a-chip B01L3/5023 takes precedence; micromixers B01F33/30; microreactors for synthesis B01J19/0093; microcapillary devices in general B81B1/00
• CPC Class Codes: B01L 3/50273 characterised by the means or forces applied to move the fluids micropumps F04B19/006, of the membrane type F04B43/043
• CPC Class Codes: B01L 3/502784 specially adapted for droplet or plug flow, e.g. digital microfluidics automatic analysis using a stream of discrete samples in a tube system G01N35/08
• CPC Class Codes: B01L 3/502792 for moving individual droplets on a plate, e.g. by locally altering surface tension
• CPC Class Codes: B41J 2002/14395 Electrowetting
• CPC Class Codes: C25B 9/00 Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
• CPC Class Codes: G01N 27/44791 Microapparatus sample containers with integrated microfluidic structures B01L3/5027
• CPC Class Codes: G02B 26/005 : based on electrowetting

Abstract

Methods are provided for manipulating droplets. The methods include providing the droplet on a surface comprising an array of electrodes and a substantially co-planer array of reference elements, wherein the droplet is disposed on a first one of the electrodes, and the droplet at least partially overlaps a second one of the electrodes and an intervening one of the reference elements disposed between the first and second electrodes. The methods further include activating the first and second electrodes to spread at least a portion of the droplet across the second electrode and deactivating the first electrode to move the droplet from the first electrode to the second electrode.

Claims

1. A binary mixing process, comprising:

(a) providing a binary mixing apparatus for mixing two droplets comprising a first binary mixing unit,

wherein the first binary mixing unit comprises an electrode array comprising X rows of electrodes and X columns of electrodes to form an electrode array consisting of X² matrix electrodes and associated cells EA_ij where _i is a positive integer that designates 1, 2, . . . X rows of electrodes, and where _j is a positive integer that designates 1, 2, . . . X columns of electrodes,

wherein the first binary mixing unit comprises a logic cell matrix comprising a subset of the rows and columns of the electrode array consisting of matrix electrodes and associated cells EA_ij in which _i and _j are both odd integers, and each cell of the logic cell matrix is capable of storing one of a sample droplet, a reagent droplet or an intermediate-mixture droplet,

wherein electrodes situated in rows of the electrode array consisting of matrix electrodes and associated cells EA_ij in which _i is an even integer comprise electrodes on which merging and/or splitting of the sample droplet, the reagent droplet, and/or the intermediate-mixture droplet occurs, and

wherein electrodes situated in columns of the electrode array consisting of matrix electrodes and associated cells EA_ij in which _j is an even integer comprise electrodes on which transport of the sample droplet, the reagent droplet, or the intermediate-mixture droplet occurs; and

(b) using the binary mixing apparatus to perform a first mixing phase comprising a row mix, a column mix, or a combination of a series of row mixes and/or column mixes of a sample droplet, a reagent droplet, and/or an intermediate-mixture droplet and to dilute the concentration of the sample droplet to a desired ratio in a series of ratios selected from the group consisting of 1;

1, 1;

3, 1;

7 . . . 1;

2^n-1, wherein n is a positive integer equal to the number of mixing operations performed.

2. The process of claim 1, wherein the binary mixing apparatus further comprises a second binary mixing unit, and a buffer in fluid communication with the first and second binary mixing units to store intermediate products and transfer intermediate products between the first and second binary mixing units.

3. The process of claim 2, wherein the second binary mixing unit comprises an electrode array comprising X rows of electrodes and X columns of electrodes to form an electrode array consisting of X² matrix electrodes and associated cells EA_ij where _i is a positive integer that designates 1, 2, . . . X rows of electrodes, and where _j is a positive integer that designates 1, 2, . . . X columns of electrodes,

wherein the second binary mixing unit comprises a logic cell matrix comprising a subset of the rows and columns of the electrode array consisting of matrix electrodes and associated cells EA_ij in which _i and _j are both odd integers, and each cell of the logic cell matrix is capable of storing one of a sample droplet, a reagent droplet, or an intermediate-mixture droplet,

wherein electrodes situated in rows of the electrode array consisting of matrix electrodes and associated cells EA_ij in which _i is an even integer comprise electrodes on which merging and/or splitting of the sample droplet, the reagent droplet, and/or the intermediate-mixture droplet occurs, and

wherein electrodes situated in columns of the electrode array consisting of matrix electrodes and associated cells EA_ij in which _j is an even integer comprise electrodes on which transport of the sample droplet, the reagent droplet, or the intermediate-mixture droplet occurs.

4. The process of claim 3, wherein the binary mixing apparatus further comprises a microprocessor capable of executing the instructions of a computer program in communication with the first binary mixing unit, second binary mixing unit, and buffer through one or more communication lines.

5. The process of claim 4, wherein the binary mixing apparatus further comprises electrode containing droplet-handling regions for each mixing unit which can be sequentially activated to implement one or more mixing operations selected from the group consisting of droplet discarding, droplet merging, droplet splitting, and combinations thereof.

6. The process of claim 5, wherein first and second binary mixing units are capable of producing a volume of droplets that is equivalent to the number of associated cells in each of the respective logic cell matrices.

7. The process of claim 6, wherein the first and second binary mixing units further comprise a sample reservoir, a waste reservoir, and a reagent reservoir in fluid communication with the electrode array.

8. The process of claim 7, wherein the first and second binary mixing units comprises a plurality of transport electrodes and associated cells for transporting droplets to and from the electrode array.

9. The process of claim 8, wherein the first binary mixing unit comprises a plurality of electrical leads connected to matrix electrodes EA_ij and the transport electrodes to control the movement or manipulation of droplets.

10. The process of claim 9, wherein the binary mixing apparatus is fabricated on a microfluidic chip.

11. The process of claims 1 or 10, wherein the first and/or second binary mixing units comprise a 7×

7 electrode array consisting of 49 matrix electrodes and associated cells EA_ij, where _i designates 1, 2, . . . , 7 rows of electrodes and _j designates 1, 2, . . . , 7 columns of electrodes.

12. The process of claim 11, wherein the binary mixing apparatus is used to perform a first single row mix by combining a sample droplet S₁ having a concentration of 1 with a reagent droplet R₁ having a concentration of 0 to produce two intermediate-mixture droplets I₁ and I₂, each intermediate-mixture droplet having ½

of the concentration of sample droplet S₁.

13. The process of claim 12, further comprising discarding at least one of intermediate-mixture droplets I₁ or I₂, and transporting a second reagent droplet R₂ having a concentration of 0 to a logic cell in the same column as, and adjacent to, the remaining intermediate-mixture droplet I₁ or I₂.

14. The process of claim 13, further comprising using the binary mixing apparatus to perform a second single row mix by combining the remaining intermediate-mixture droplet I₁ or I₂ and the second reagent droplet R₂ to produce two intermediate-mixture droplets I₃ or I₄, each intermediate-mixture droplet having ¼

of the concentration of sample droplet S₁.

15. The process of claim 14, further comprising transporting a third reagent droplet R₃ and a fourth reagent droplet R₄, each having a concentration of 0, to logic cells in the same column as, and adjacent to, the intermediate-mixture droplets I₃ and I₄.

16. The process of claim 15, further comprising using the binary mixing apparatus to perform a double row mixing operation by combining the intermediate-mixture droplets I₃ and I₄ with the respective reagent droplets R₃ and R₄ to produce four intermediate-mixture droplets I₅, I₆, I₇, and I₈, each intermediate-mixture droplet having ⅛

of the concentration of sample droplet S₁.

17. The process of claim 16, further comprising transporting a fifth reagent droplet R₅, a sixth reagent droplet R₆, a seventh reagent droplet R₇, and an eighth reagent droplet R₈, each having a concentration of 0, to logic cells in a different column than, and adjacent to, the intermediate-mixture droplets I₅, I₆, I₇, and I₈.

18. The process of claim 17, further comprising using the binary mixing apparatus to perform a first column mix operation between each corresponding pair of intermediate-mixture droplets I₅, I₆, I₇, and I₈ and reagent droplets R₅, R₆, R₇, and R₈ to produce eight intermediate-mixture droplets I₉, I₁₀, I₁₁, I₁₂, I₁₃, I₁₄, I₁₅ and I₁₆, each having 1/16 of the concentration of sample droplet S₁, wherein intermediate-mixture droplets I₉, I₁₀, I₁₁, and I₁₂ are produced in a first column of the logic cell matrix, and intermediate-mixture droplets I₁₃, I₁₄, I₁₅ and I₁₆ are produced in a second column of the logic cell matrix.

19. The process of claim 18, further comprising transporting each intermediate-mixture droplet in the first and second columns of the logic cell matrix to the next adjacent column to the right in the logic cell matrix.

20. The process of claim 19, further comprising transporting four reagent droplets R₉, R₁₀, R₁₁ and R₁₂, each having a concentration of 0, to a column in the logic ceil matrix that is adjacent to corresponding intermediate-mixture droplets I₉, I₁₀, I₁₁, and I₁₂, and transporting four reagent droplets R₁₃, R₁₄, R₁₅, and R₁₆, each having a concentration of 0, to a column in the logic cell matrix that is adjacent to corresponding intermediate-mixture droplets I₁₃, I₁₄, I₁₅, and I₁₆.

21. The process of claim 19, further comprising using the binary mixing apparatus to perform a double column mix operation between each corresponding pair of intermediate-mixture droplets I₉, I₁₀, I₁₁, I₁₂ and reagent droplets R₁₃, R₁₄, R₁₅, and R₁₆ and each corresponding pair of intermediate-mixture droplets I₁₃, I₁₄, I₁₅, and I₁₆ and reagent droplets R₁₃, R₁₄, R₁₅, and R₁₆ to produce sixteen final-mixture product droplets P₁, P₂, P₃, P₄, P₅, P₆, P₇, P₈, P₉, P₁₀, P₁₁, P₁₂, P₁₃, P₁₄, P₁₅ and P₁₆, each having 1/32 of the concentration of sample droplet S₁.

22. The process of claim 21, wherein the product droplets P₁-P₁₆ are used for sampling, detection, and/or analysis.

23. The process of claim 22, further comprising using the binary mixing apparatus to perform a second mixing phase comprising a row mix, a column mix, or a combination of a series of row mixes and/or column mixes of a sample droplet, a reagent droplet, and/or an intermediate-mixture droplet and to dilute the concentration of the sample droplet to a desired ratio in a series of ratios selected from the group consisting of 1:

1, 1;

3, 1;

7 . . . 1;

2^n-1, wherein n is a positive integer equal to the number of mixing operations performed.

24. The process of claim 23, wherein the second mixing phase is performed using the second binary mixing unit in parallel to, and independent of, the first mixing phase using the first binary mixing unit.

25. The process of claim 24, further comprising performing an additional mixing phase using products from a previous mixing phase to calibrate a mixing ratio for increased accuracy.

26. The process of claim 22, wherein the first binary mixing unit comprises a first surface area and the array of electrodes comprises a first array of electrodes disposed in at least a substantially co-planar relation on the first surface area, wherein the first array of electrodes comprises first drive electrodes and dedicated first reference electrodes.

27. The process of claim 26, wherein the binary mixing apparatus further comprises an electrode selector for dynamically creating a sequence of first electrode pairs on the first surface area, each first electrode pair comprising a selected first electrode pair comprising a selected first drive electrode biased to a first voltage and a selected first reference electrode biased to a second voltage less than the first voltage.

28. The process of claim 27, wherein the second binary mixing unit comprises a second surface area and the array of electrodes comprises a second array of electrodes disposed in at least a substantially co-planar relation on the second surface area, and a droplet outlet area communicating with the second surface area and with the first mixing unit, wherein the second array of electrodes comprises second drive electrodes and dedicated second reference electrodes.

29. The process of claim 28, wherein the electrode selector dynamically creates a sequence of second electrode pairs on the second surface area, each second electrode pair comprising a selected second drive electrode biased to a third voltage and a selected second reference electrode biased to a fourth voltage less than the third voltage.

30. The process of claim 29, wherein the electrode selector sequentially activates and de-activates one or more selected first drive electrodes to mix together two droplets supplied to the first surface area.

31. The process of claim 30, wherein the electrode selector sequentially activates and de-activates one or more selected second drive electrodes to mix together two other droplets supplied to the second surface area.

32. The process of claim 31, wherein mixing of the two droplets supplied to the first surface area is accomplished by electrowetting actuation wherein the droplets overlap a selected first drive electrode biased to a first voltage and a selected first reference electrode biased to a second voltage continuously.

33. The process of claim 32, wherein mixing of the two droplets supplied to the second surface area is accomplished by electrowetting actuation wherein the droplets overlap a selected second drive electrode biased to a second voltage and a selected second reference electrode biased to a second voltage continuously.

34. The process of claim 1, wherein the binary mixing apparatus further comprises:

(a) a substrate comprising a substrate surface;

(b) the electrode array, wherein the X rows of electrodes and X columns of electrodes comprise drive electrodes disposed on the substrate surface;

(c) a dedicated array of reference elements settable to a common reference potential and disposed in at least substantially co-planar relation to the electrode array, wherein the array of reference elements is electrically and physically distinct from the drive electrode array and further wherein each drive electrode is adjacent to at least one of the reference elements;

(d) a dielectric layer disposed on the substrate surface to cover the drive electrodes; and

(e) an electrode selector for sequentially activating and de-activating one or more selected drive electrodes of the array to sequentially bias the selected drive electrodes to an actuation voltage, whereby a droplet disposed on the substrate surface moves along a desired path defined by the selected drive electrodes.

35. The process according to claim 34, wherein the binary mixing apparatus further comprises a plate spaced from the substrate surface by a distance to define a space between the plate and the substrate surface, wherein the distance is sufficient to contain a droplet disposed in the space.

36. The process according to claim 35, wherein the plate comprises a plate surface facing the substrate surface, and the plate surface is hydrophobic.

37. The process according to claim 35, wherein the binary mixing apparatus further comprises a filler fluid disposed in the space.

38. The process according to claim 34, wherein at least outer portions of the drive electrodes and the reference elements are respectively hydrophobized.

39. The process according to claim 34, wherein the binary mixing apparatus further comprises a hydrophobic film disposed on the drive electrodes and the reference elements.

40. The process according to claim 34, wherein the array of reference elements comprises a grid of elongate structures.

41. The process according to claim 34, wherein the reference elements are set to a reference voltage less than the actuation voltage.

42. The process according to claim 34, wherein the reference elements are set to ground potential.

43. The process according to claim 34, wherein at least a portion of the dielectric layer is hydrophobic.

44. The process according to claim 34, wherein the electrode selector comprises an electronic processor.

45. The process according to claim 34, wherein the binary mixing apparatus further comprises a droplet inlet communicating with the substrate surface.

46. The process according to claim 45, wherein the binary mixing apparatus further comprises a droplet outlet communicating with the substrate surface.