Optical microfluidic devices and methods

• US 20030047688A1
• Filed: 08/07/2002
• Published: 03/13/2003
• Est. Priority Date: 08/07/2001
• Status: Active Grant

• Current Assignee: SRI International, Inc.
• Original Assignee: SRI International, Inc.
• Inventors: Wright, William H., Heydt, Richard P., Faris, Gregory W., Bashkin, John S., MacQueen, David
• Granted Patent: US 6,734,436 B2
• Time in Patent Office: Days
• US Class Current: 250/432R
• CPC Class Codes: B01L 2200/142 Preventing evaporation
• 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 2400/0454 radiation pressure, optical tweezers
• CPC Class Codes: B01L 3/502792 for moving individual droplets on a plate, e.g. by locally altering surface tension
• CPC Class Codes: G01N 15/0255 with mechanical, e.g. inertial, classification, and investigation of sorted collections with centrifuges G01N15/042
• CPC Class Codes: Y10T 436/25 including sample preparation

Abstract

The invention relates to microfluidic devices and methods that employ electromagnetic radiation to move a droplet of fluid on a fluid-transporting surface of a substrate. Typically, radiation of a particular wavelength is directed through a substantially transparent material, and the radiation imparts an optical trapping force to move the droplet. In addition, a means for reducing evaporative loss from the droplet may be provided.

Claims

1. An optical microfluidic device, comprising:

a solid substrate comprised of a material that is substantially transparent to electromagnetic radiation of a particular wavelength, the substrate having a fluid-transporting surface and an opposing electromagnetic radiation-receiving surface;

an electromagnetic radiation source for generating electromagnetic radiation having the particular wavelength; and

a means for directing electromagnetic radiation generated by the source toward the radiation-receiving surface and through the substrate to the fluid-transporting surface in a manner effective to optically move at least one droplet of a selected fluid on the fluid-transporting surface from a first site to a second site.

2. The device of claim 1, wherein the means for directing electromagnetic radiation is adapted to optically move a plurality of droplets on the fluid-transporting surface.

3. The device of claim 2, wherein the means for directing electromagnetic radiation is adapted to optically move the droplets in succession.

4. The device of claim 2, wherein the means for directing electromagnetic radiation is adapted to optically move the droplets simultaneously.

5. The device of claim 1, further comprising a means for tracking and/or locating the at least one droplet.

6. The device of claim 1, wherein the fluid-transporting surface is substantially planar.

7. The device of claim 6, wherein the fluid-transporting surface and the radiation-receiving surface are parallel to each other.

8. The device of claim 1, wherein the substrate is optically homogeneous with respect to electromagnetic radiation of the particular wavelength.

9. The device of claim 1, wherein the fluid-transporting surface is comprised of a plurality of regions, each exhibiting a different degree of affinity for the selected fluid so as to form different contact angles with the selected fluid.

10. The device of claim 1, further comprising a means for constraining the selected fluid.

11. The device of claim 10, wherein the means for constraining the selected fluid is adapted to constrain any droplet not being optically moved by the directed electromagnetic radiation.

12. The device of claim 10, wherein the means for constraining the selected fluid comprises a fluid-constraining feature on the fluid-transporting surface.

13. The device of claim 12, wherein the fluid-constraining feature is comprised of a first surface region circumscribing a second surface region, the second surface region exhibiting a higher degree of affinity for the selected fluid than the first surface region such that the second surface region forms a smaller contact angle with the selected fluid than the first surface region.

14. The device of claim 12, wherein the fluid-constraining feature comprises an indentation or protrusion on the fluid-transporting surface.

15. The device of claim 12, comprising a plurality of fluid-constraining features on the fluid-transporting surface.

16. The device of claim 15, wherein the fluid-constraining features are arranged in an array on the fluid-transporting surface.

17. The device of claim 1, wherein the fluid-transporting surface is coated at least in part with a lubricating layer.

18. The device of claim 17, wherein the lubricating layer is comprised of a fluid composition that is nonreactive and immiscible with the selected fluid.

19. The device of claim 18, wherein the fluid composition is hydrophobic.

20. The device of claim 1, wherein at least a portion of the fluid-transporting surface is comprised of a hydrophobic region.

21. The device of claim 20, wherein the hydrophobic region comprises a hydrophobic moiety bound to the fluid-transporting surface.

22. The device of claim 21, wherein the hydrophobic moiety is selected from the group consisting of silanes, siloxanes, fluorosilanes, fluorosiloxanes, hydrocarbons, fluorocarbons, combinations thereof, and polymers and copolymers of any of the foregoing.

23. The device of claim 20, wherein the hydrophobic region is a textured surface.

24. The device of claim 1, wherein a contact angle of at least about 130°

is formed between the at least one droplet and the fluid-transporting surface.

25. The device of claim 24, wherein the contact angle is at least about 150°

.

26. The device of claim 25, wherein the contact angle is at least about 170°

.

27. The device of claim 1, wherein the source of electromagnetic radiation produces substantially monochromatic radiation.

28. The device of claim 27, wherein the source of electromagnetic radiation is a laser.

29. The device of claim 1, wherein the source of electromagnetic radiation is a light emitting diode.

30. The device of claim 1, comprising a single source of electromagnetic radiation.

31. The device of claim 1, wherein the particular wavelength corresponds to a wavelength that is minimally absorbed by the selected fluid.

32. The device of claim 1, wherein the means for directing electromagnetic radiation is selected from the group consisting of mirror and galvo systems, acoustic-optic deflector systems, liquid crystal-based deflector systems, microelectromechanical mirror systems, and combinations of any of the foregoing.

33. The device of claim 1, further comprising a means for reducing evaporative loss from the at least one droplet of the selected fluid.

34. The device of claim 33, wherein the means for reducing evaporative loss is comprised of a vapor-blocking layer that is substantially impermeable to the selected fluid in vapor form, wherein the vapor-blocking layer is positioned in facing and, optionally, contacting relationship with respect to the fluid-transporting surface.

35. The device of claim 34, wherein the vapor-blocking layer is comprised of a fluid composition that is immiscible and nonreactive with the selected fluid.

36. The device of claim 34, wherein the vapor-blocking layer is comprised of a solid material.

37. The device of claim 1, further comprising a means for introducing the selected fluid in vapor form at or near the fluid-transporting surface.

38. The device of claim 1, wherein the selected fluid is aqueous.

39. An optical microfluidic device, comprising:

a solid substrate having a fluid-transporting surface;

an optically homogeneous cover plate comprised of a material that is substantially transparent to electromagnetic radiation of a particular wavelength, the cover plate having an electromagnetic radiation-receiving surface and an opposing surface that faces the fluid-transporting surface;

an electromagnetic radiation source for generating electromagnetic radiation having the particular wavelength; and

a means for directing electromagnetic radiation generated by the source toward the radiation-receiving surface and through the cover plate to the fluid-transporting surface in a manner effective to optically move at least one droplet of a selected fluid on the fluid-transporting surface from a first site to a second site.

40. An optical microfluidic device, comprising:

a solid substrate having a fluid-transporting surface;

an electromagnetic radiation source for generating electromagnetic radiation; and

a means for directing electromagnetic radiation generated by the source toward the fluid-transporting surface in a manner effective to optically move at least one droplet of a selected fluid on the fluid-transporting surface from a first site to a second site; and

a means for reducing evaporative loss from the at least one fluid droplet.

41. The device of claim 40, wherein the fluid-transporting surface is substantially planar.

42. The device of claim 40, wherein the selected fluid is aqueous.

43. The device of claim 40, wherein the means for reducing evaporative loss is comprised of a vapor-blocking layer that is substantially impermeable to the selected fluid in vapor form, wherein the vapor-blocking layer is positioned in facing and, optionally, contacting relationship with respect to the fluid-transporting surface.

44. The device of claim 43, wherein the vapor-blocking layer is comprised of a fluid composition that is nonreactive and immiscible with the selected fluid.

45. The device of claim 44, further comprising a cover plate facing the fluid-transporting layer of the substrate, wherein the vapor-blocking layer is interposed between the cover plate and the substrate.

46. The device of claim 43, wherein the vapor-blocking layer is comprised of a solid material.

47. The device of claim 43, wherein the vapor-blocking layer is comprised of a substantially transparent material through which the electromagnetic radiation is directed.

48. The device of claim 47, wherein the vapor-blocking layer is optically homogeneous with respect to electromagnetic radiation of the particular wavelength.

49. The device of claim 40, further comprising a means for introducing the selected fluid in vapor form at or near the fluid-transporting surface.

50. A method for controllably moving a droplet of a selected fluid across a surface of a solid substrate, comprising:

(a) depositing a droplet of a selected fluid on a solid substrate having a fluid-transporting surface and an opposing electromagnetic radiation-receiving surface, wherein the substrate is comprised of a material that is substantially transparent to electromagnetic radiation of a particular wavelength, and the droplet is placed on a first site of the fluid-transporting surface; and

(b) directing electromagnetic radiation having a particular wavelength toward the radiation-receiving surface and through the substrate to the fluid-transporting surface in a manner effective to optically move the droplet to a second site on the fluid-transporting surface.

51. The method of claim 50, wherein the fluid-transporting surface is coated at least in part with a lubricating layer and the droplet is placed on the lubricating layer.

52. The method of claim 51, wherein the lubricating layer is comprised of a fluid composition that is nonreactive and immiscible with the selected fluid.

53. The method of claim 52, wherein the fluid composition is hydrophobic.

54. The method of claim 50, wherein the droplet is free from vesicles, microspheres, or liposomes.

55. The method of claim 50, wherein the droplet is comprised of a vesicle, microsphere, or liposome.

56. The method of claim 50, wherein the droplet contains a plurality of solid particles.

57. The method of claim 56, wherein at least some or all of the solid particles are located on a surface of the droplet.

58. The method of claim 56, wherein at least some or all of the solid particles are located within the droplet.

59. The method of claim 50, wherein a contact angle of at least about 130°

is formed between the droplet and the fluid-transporting surface.

60. The method of claim 59, wherein the contact angle is at least about 150°

.

61. The method of claim 60, wherein the contact angle is at least about 170°

.

62. The method of claim 50, wherein the droplet is optically moved away from the fluid-transporting surface during step (b).

63. The method of claim 50, further comprising, after (a), splitting the droplet into two droplets.

64. The method of claim 50, wherein the droplet has a volume of no greater than about 10 nanoliters.

65. The method of claim 64, wherein the droplet has a volume of no greater than about 100 picoliters.

66. The method of claim 65, wherein the droplet has a volume of no greater than about 1 picoliter.

67. The method of claim 50, further comprising reducing evaporative loss from the droplet while the droplet is on the fluid-transporting surface.

68. The method of claim 67, wherein evaporative loss is reduced by placing a vapor-blocking layer that is substantially impermeable to the selected fluid in vapor form over the droplet and the fluid-transporting surface so as to suppress release of the selected fluid in vapor form from the droplet.

69. The method of claim 68, wherein the vapor-blocking layer is comprised of a fluid composition that is immiscible and nonreactive with the selected fluid.

70. The method of claim 68, wherein the vapor-blocking layer is comprised of a solid material.

71. The method of claim 68, wherein evaporative loss is reduced by introducing the selected fluid in vapor form at or near the fluid-transporting surface.

72. The method of claim 50, wherein different contact angles are formed between the droplet and the fluid-transporting surface at the first and second sites.

73. The method of claim 50, wherein the same contact angle is formed between the droplet and the fluid-transporting surface at the first and second sites.

74. The method of claim 50, wherein the droplet is merged with additional fluid at the second site.

75. The method of claim 50, wherein the droplet contains a moiety that selectively binds to the fluid-transporting surface while the droplet is moved from the first to the second site.

76. The method of claim 50, wherein the directed radiation exhibits a Gaussian intensity profile.

77. The method of claim 50, wherein the directed radiation exhibits a non-Gaussian intensity profile.

78. The method of claim 50, wherein the directed radiation exhibits a rotationally symmetric intensity profile.

79. The method of claim 50, wherein the directed radiation exhibits a laterally symmetric intensity profile.

80. The method of claim 50, wherein the droplet is comprised of an aqueous liquid.

81. The method of claim 50, wherein the droplet contains a biomolecule.

82. The method of claim 50, wherein the biomolecule is peptidic or nucleotidic.

83. A method for controllably moving a droplet of a selected fluid across a surface of a solid substrate, comprising:

(a) depositing the droplet of a selected fluid on a first site of a fluid-transporting surface of a solid substrate;

(b) placing an optically homogeneous cover plate comprised of a material that is substantially transparent to electromagnetic radiation of a particular wavelength over the fluid-transporting surface, wherein the cover plate has an electromagnetic radiation-receiving surface and an opposing surface that is positioned in facing relationship to the fluid-transporting surface; and

(c) directing electromagnetic radiation having a particular wavelength toward the radiation-receiving surface and through the cover plate to the fluid-transporting surface in a manner effective to optically move the droplet to a second site on the fluid-transporting surface.

84. A method for controllably moving a droplet of a selected fluid across a surface of a solid substrate, comprising:

(a) depositing the droplet of a selected fluid on a first site of a fluid-transporting surface of a solid substrate;

(b) directing electromagnetic radiation having a particular wavelength to the fluid-transporting surface in a manner effective to optically move the droplet to a second site on the fluid-transporting surface; and

(c) reducing evaporative loss from the droplet while the droplet is on the fluid-transporting surface.

85. A method for controllably moving a fluid droplet across an interior surface of an enclosure, wherein the enclosure is formed at least in part by an optically homogeneous solid wall comprised of a material that is substantially transparent to electromagnetic radiation of a particular wavelength, comprising:

(a) depositing a droplet of a selected fluid on the interior surface of the enclosure at a first site; and

(b) directing electromagnetic radiation of the particular wavelength through the solid wall in a manner effective to optically move the droplet across the interior surface to the second site.

86. The method of claim 85, wherein the enclosure is a tube.