Methods and systems for dispensing sub-microfluidic drops

• US 20050056713A1
• Filed: 08/02/2004
• Published: 03/17/2005
• Est. Priority Date: 07/31/2003
• Status: Active Grant

• Current Assignee: BioDot, Inc. (ATS Corp.)
• Original Assignee: BioDot, Inc. (ATS Corp.)
• Inventors: Tisone, Thomas C., Rodriquez, Michelle, Cabourne, Michael K.
• Granted Patent: US 7,470,547 B2
• Time in Patent Office: Days
• US Class Current: 239/690
• CPC Class Codes: B01D 19/0047 Atomizing, spraying, trickling
• CPC Class Codes: B01J 19/0046 Sequential or parallel reactions, e.g. for the synthesis of polypeptides or polynucleotides; Apparatus and devices for combinatorial chemistry or for making molecular arrays synthesis methods per se C40B50/00
• CPC Class Codes: B01J 2219/00369 in multiple or parallel arrangements
• CPC Class Codes: B01J 2219/00371 comprising electrodes
• CPC Class Codes: B01J 2219/00409 Solenoids in combination with valves
• CPC Class Codes: B01J 2219/00412 In multiple arrangements
• CPC Class Codes: B01J 2219/00527 Sheets
• CPC Class Codes: B01J 2219/00605 the compounds being directly bound or immobilised to solid supports
• CPC Class Codes: B01J 2219/0061 The surface being organic
• CPC Class Codes: B01J 2219/00612 the surface being inorganic
• CPC Class Codes: B01J 2219/00637 by coating it with another layer
• CPC Class Codes: B01J 2219/00659 Two-dimensional arrays
• CPC Class Codes: B01J 2219/00691 using robots
• CPC Class Codes: B01L 2400/027 electrostatic forces between substrate and tip
• CPC Class Codes: B01L 2400/0478 pistons
• CPC Class Codes: B01L 2400/0487 fluid pressure, pneumatics
• CPC Class Codes: B01L 2400/0622 distribution valves, valves having multiple inlets and/or outlets, e.g. metering valves, multi-way valves
• CPC Class Codes: B01L 3/0241 Drop counters; Drop formers making arrays for combinatorial libraries B01J19/0046; automation of dispensing for analysis G01N35/10
• CPC Class Codes: B01L 3/0265 using valves to interrupt or meter fluid flow, e.g. using solenoids or metering valves
• CPC Class Codes: B01L 3/0268 using pulse dispensing or spraying, eg. inkjet type, piezo actuated ejection of droplets from capillaries
• CPC Class Codes: B05B 1/3053 : the actuating means being a solenoid
• CPC Class Codes: B05B 15/658 : the spraying apparatus or its outlet axis being perpendicular to the flow conduit
• CPC Class Codes: B05B 17/0607 : generated by electrical means, e.g. piezoelectric transducers
• CPC Class Codes: B05B 5/025 : Discharge apparatus, e.g. electrostatic spray guns
• CPC Class Codes: B05B 5/16 : Arrangements for supplying liquids or other fluent material
• CPC Class Codes: B05B 9/0423 : for supplying liquid or other fluent material to several spraying apparatus
• CPC Class Codes: G01N 35/1002 : Reagent dispensers
• CPC Class Codes: Y10T 436/2575 : Volumetric liquid transfer

Abstract

The invention relates generally to dispensing of fluids and, in particular, to methods and systems for dispensing microfluidic or sub-microfluidic volumes of droplets of chemical, biological or other reagents or liquids. Embodiments of the invention have particular efficacy in accurately dispensing small drops having volumes from about 100 nL down into the picoliter range.

Claims

1. A method of accurately dispensing sub-microfluidic droplets of a reagent, comprising:

providing a dispenser connected to a dispensing tip having a nozzle and a droplet emitting orifice at a distal end;

generating an electric field between said tip and an alignment member so that an electric field gradient is created substantially parallel to the intended droplet trajectory; and

actuating said dispenser to dispense one or more droplets of a reagent into or onto a target.

2. The method of claim 1, wherein said alignment member comprises a tube intermediate said tip and said target.

3. The method of claim 1, wherein said alignment member comprises a nest or table on which said target is seated.

4. The method of claim 1, wherein said electric field perturbs the fluid meniscus at said orifice to form a Taylor cone and said method further includes applying a superimposed positive displacement pulse to aid in ejection of said droplets from said orifice.

5. The method of claim 1, wherein said method further includes maintaining a voltage difference between said nozzle and said reagent therein.

6. The method of claim 5, wherein said nozzle has an outer surface coated with a conductive layer except for a portion at said distal end of said tip.

7. The method of claim 1, wherein said method further includes flowing ionized air over said nozzle to induce a hydrophobic effect.

8. The method of claim 1, wherein said dispenser comprises a solenoid-actuated dispenser and is driven by a hydraulic source.

9. The method of claim 8, wherein said hydraulic source comprises a positive displacement pump.

10. The method of claim 1, wherein said dispenser is driven by a pneumatic source.

11. The method of claim 10, wherein said dispenser is a solenoid-actuated dispenser.

12. The method of claim 1, wherein said droplets have a volume in the range from about 1 nL to about 100 nL.

13. The method of claim 1, wherein said droplets have a volume of about 1 nL.

14. The method of claim 1, wherein said droplets have a volume in the picoliter range.

15. The method of claim 1, wherein said electric field is in the range from about 0.5 kV to about 50 kV.

16. The method of claim 1, wherein said target comprises a substrate with a conductive layer.

17. The method of claim 1, wherein said target comprises a substrate with a functional coating which is conductive.

54. The method of claim 1, wherein said method further comprises providing an elastic element in the fluid path.

18. A method of accurately dispensing sub-microfluidic droplets of a reagent onto or onto a target supported on a table, comprising:

providing a dispensing system comprising a substantially inert fluid path and a dispensing tip having a nozzle and a droplet emitting orifice at a distal end;

generating an electric field between said tip and said table by maintaining said tip at a first potential and said table at a second potential; and

positively displacing said liquid through said tip to dispense droplets onto or into said target with said electric field providing a bias that facilitates droplet ejection and release from said tip so that droplets having a volume of less than about one microliter are reliably dispensed.

19. The method of claim 18, wherein said electric field provides a gradient substantially parallel to the intended droplet trajectory.

20. The method of claim 18, wherein said method further comprises providing a ring electrode at a third potential and positioned intermediate said tip and said target and/or table.

21. The method of claim 20, wherein said method further comprises adjusting said first, second and third potentials to control droplet impact velocity on said target.

22. The method of claim 20, wherein said first and said second potentials are substantially the same while said third potential is lower so that droplet impact velocity is substantially a function of ejection velocity.

23. The method of claim 20, wherein said first potential is lower than said second potentials while said third potential is lower than both so that droplet impact velocity is reduced compared to that without any electric field.

24. The method of claim 18, wherein said electric field perturbs the fluid meniscus at said orifice to form a Taylor cone and said method further comprises applying a superimposed positive displacement pulse to aid in ejection of said droplets from said orifice.

25. The method of claim 18, wherein said method further comprises maintaining a voltage difference between said nozzle and said liquid therein.

26. The method of claim 25, wherein said nozzle has an outer surface coated with a conductive layer except for a portion at said distal end of said tip.

27. The method of claim 18, wherein said method further comprises flowing ionized air over said nozzle to induce a hydrophobic effect.

28. The method of claim 18, wherein said method further comprises controlling the surface charge on said target.

29. The method of claim 18, wherein a hydraulic source positively displaces said liquid.

30. The method of claim 18, wherein a pneumatic source positively displaces said liquid.

31. The method of claim 18, wherein said droplets have a volume less than about 100 nanoliters.

32. The method of claim 18, wherein said electric field is in the range from about 0.5 kV to about 5 kV.

33. The method of claim 20, wherein said ring electrode is integrated with said tip.

34. The method of claim 20, wherein said ring electrode is movable from under said tip.

35. The method of claim 18, wherein positive displacement pulses provide said liquid to said tip.

36. The method of claim 35, wherein said displacement pulses are substantially synchronized with motion of said tip and/or said target.

37. The method of claim 35, wherein said method further comprises providing electric field pulses.

38. The method of claim 37, wherein said field pulses are substantially synchronized with said displacement pulses.

39. The method of claim 37, wherein said field pulses and said displacement pulses are offset by a phase lag or lead.

40. The method of claim 37, wherein said field pulses and said displacement pulses are substantially synchronized with motion of said tip and/or said target.

41. The method of claim 37, wherein said pulses are variable in pulse time and magnitude.

42. The method of claim 18, wherein said method further comprises providing an array of tips.

43. The method of claim 42, wherein adjacent tips are spaced by at least 2 mm.

44. The method of claim 18, wherein said method further comprises pressurizing a reservoir containing said liquid to be dispensed to a degassing high first pressure by providing a static pressure from a helium source over said liquid to degas said liquid.

45. The method of claim 44, wherein said method further comprises reducing said first pressure in said reservoir to a low second pressure.

46. The method of claim 45, wherein said method further comprises venting said reservoir to ambient conditions.

47. The method of claim 45, wherein said method further comprises operating a pump connected to said reservoir to draw said liquid from said reservoir into said pump.

48. The method of claim 18, wherein said tip has a first conduit and a second conduit having a drop emitting orifice with said conduits being angled with respect to one another.

49. The method of claim 48, wherein said tip comprises a shaped surface proximate to a junction between said conduits to direct said liquid from said first conduit towards said orifice.

50. The method of claim 49, wherein said first conduit and said second conduit are substantially perpendicular to one another.

51. The method of claim 50, wherein said shaped surface comprises a substantially uniform bevel.

52. The method of claim 51, wherein said bevel is angled relative to said first and said second conduits by an angle substantially equal to half the angle between said first and said second conduits.

53. The method of claim 50, wherein said shaped surface comprises a contoured and/or curved surface.

55. The method of claim 18, wherein said method further comprises providing a constrictor in the fluid path.

56. The method of claim 18, wherein said method further comprises providing a dampener in the fluid path.

57. A method of accurately dispensing sub-microfluidic droplets of a reagent, comprising:

pressurizing a reservoir containing a reagent to a degassing high first pressure by providing a static pressure from a helium source over said reagent to degas said reagent;

reducing said first pressure in said reservoir to a low second pressure;

venting said reservoir to ambient conditions;

operating a pump connected to said reservoir to draw said reagent from said reservoir into said pump;

providing a tip having a dispense nozzle and a through lumen with said tip being connected to said pump; and

metering a predetermined quantity of said reagent from said pump to said tip to dispense one or more droplets of said reagent from said nozzle onto or into a target.

58. The method of claim 57, wherein pressurizing said reservoir and venting said reservoir are repeated a predetermined number of times.

59. The method of claim 57, wherein said first pressure is in the range from about 0.1 psig to about 50 psig.

60. The method of claim 57, wherein said second pressure is about 0.1 psig.

61. The method of claim 57, wherein during dispensing said reservoir is maintained at a low third pressure by providing a static helium pressure over said reagent.

62. The method of claim 61, wherein said third pressure is about 0.1 psig.

63. The method of claim 57, wherein prior to venting said reservoir a valve is switched so that said reservoir is in fluid communication with a vent line and fluidly isolated from said helium source.

64. The method of claim 57, wherein prior to dispensing a valve is switched so that said pump is in fluid communication with said tip and fluidly isolated from said reservoir.

65. The method of claim 57, wherein metering a predetermined quantity of said reagent further comprises metering a predetermined quantity of said reagent from said pump to a dispenser intermediate said pump and said tip.

66. The method of claim 65, wherein said method further comprises operating said dispenser to facilitate ejection of said one or more droplets of said reagent onto or into said target.

67. The method of claim 66, wherein prior to droplet ejection the hydraulic pressure within said pump and said dispenser is adjusted to substantially steady state conditions.

68. The method of claim 57, wherein said droplets have a volume in the range from about 1 nL to about 100 nL.

69. The method of claim 57, wherein said droplets have a volume of about 1 nL.

70. The method of claim 57, wherein said droplets have a volume in the picoliter range.

71. The method of claim 57, wherein said method further includes providing a manifold intermediate said helium source and a plurality of reservoirs containing reagents so that each of the reagents can be independently or simultaneously degassed.

72. An apparatus for dispensing droplets of a reagent on a target that is not easily accessible, comprising:

a dispenser having an inlet and an outlet and a valve adapted to be opened and closed at a predetermined frequency and duty cycle;

a positive displacement pump hydraulically arranged in series with said inlet of said dispenser for metering predetermined quantities of a reagent to said dispenser;

a dispense tip connected to said outlet of said dispenser to eject droplets of said reagent onto or into a substrate target, comprising;

a first conduit originating at said outlet end of said dispenser and extending away from said outlet end of said dispenser, said first conduit having a first axis;

a second conduit extending to form a droplet emitting orifice and in fluid communication with said first conduit at a common junction, said second conduit having a second axis angled relative to said first axis; and

a shaped surface proximate to said junction between said conduits to direct said reagent from said first conduit towards said orifice.

73. The apparatus of claim 72, wherein said first axis and said second axis are substantially perpendicular to one another.

74. The apparatus of claim 72, wherein said shaped surface comprises a substantially uniform bevel.

75. The apparatus of claim 74, wherein said bevel is angled relative to said first and said second axes by an angle substantially equal to half the angle between said first and said second axes.

76. The apparatus of claim 72, wherein said shaped surface comprises a contoured and/or curved surface.