Control of electrolysis gases in electroosmotic pump systems

• US 7,134,486 B2
• Filed: 10/16/2002
• Issued: 11/14/2006
• Est. Priority Date: 09/28/2001
• Status: Expired due to Fees

• Current Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford Management Co.)
• Original Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford Management Co.)
• Inventors: Zeng, Shulin, Santiago, Juan G.
• Primary Examiner(s): Walberg, Teresa J.
• Application Number:
  US10/272,048
• Publication Number:
  US 20030085024A1
• Time in Patent Office: 1,490 Days
• Field of Search: 165/104.33, 165/104.25, 165/104.28, 417/41, 625/15, 624/80, 622/592
• US Class Current: 165/104.28
• CPC Class Codes: B01D 19/0031 by filtration
• CPC Class Codes: B01D 61/427 Electro-osmosis
• CPC Class Codes: B01D 67/0062 by micromachining techniques, e.g. using masking and etching steps, photolithography
• CPC Class Codes: F04B 19/006 Micropumps F04B43/043 and F04B43/095 take precedence
• CPC Class Codes: F28D 15/00 Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies F28D17/00, F28D19/00, F28D20/00 take precedence
• CPC Class Codes: F28D 15/043 forming loops, e.g. capillary pumped loops
• CPC Class Codes: F28D 15/06 Control arrangements therefor
• CPC Class Codes: F28F 2260/02 having microchannels
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48145 the bodies being stacked
• CPC Class Codes: H01L 2224/73257 Bump and wire connectors
• CPC Class Codes: H01L 2225/06562 at least one device in the stack being rotated or offset
• CPC Class Codes: H01L 23/473 by flowing liquids H01L23/4332, H01L23/4338 take precedence
• CPC Class Codes: H01L 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details

Abstract

Apparatus and methods according to the present invention preferably utilize electroosmotic pumps that are capable of generating high pressure and flow without moving mechanical parts and the associated generation of unacceptable electrical and acoustic noise, as well as the associated reduction in reliability. These electroosmotic pumps are preferably fabricated with materials and structures that improve performance, efficiency, and reduce weight and manufacturing cost relative to presently available micropumps. These electroosmotic pumps also preferably allow for control including venting or recapture of evolved gases and deposited materials, which may provide for long-term closed-loop operation. A gas permeable membrane removes and vents electrolytic gasses generated within the fluid chamber of the electroosmotic pump to ambient. A catalyst can be used to recombine electrolytic gases to form a vapor product that can be vented or condensed into a liquid state. An osmotic membrane provides for re-entry of condensed fluid to the fluid chamber.

Claims

1. An electroosmotic pump system that pumps a fluid having a liquid phase through a closed loop upon application of an electric field, comprising:

a fluid chamber having a fluid inlet and a fluid outlet;

an anode disposed within an anode chamber portion;

a cathode disposed within a cathode chamber portion;

a structure that provides electroosmotic pumping upon application of the electric field between the anode and cathode, the structure creating a partition in the fluid chamber between the anode chamber portion and the cathode chamber portion;

a gas permeable membrane to vent electrolytic gases generated within the fluid chamber, the gas permeable membrane disposed in a wall of the fluid chamber; and

a catalyst for recombining at least part of the electrolytic gases.

2. The electroosmotic pump system of claim 1 wherein the gas-permeable membrane is disposed in a wall of the anode chamber portion and located above the fluid inlet.

3. The electroosmotic pump system of claim 1 wherein the gas-permeable membrane vents electrolytic gases to an environment in which the pump operates.

4. The electroosmotic pump system of claim 1 wherein the gas-permeable membrane vents electrolytic gases to ambient.

5. The electroosmotic pump system of claim 1 wherein the electrolytic gases removed are hydrogen and oxygen.

6. The electroosmotic pump system of claim 1 wherein the fluid is deionized water.

7. The electroosmotic pump system of claim 1 further comprising an additional gas permeable membrane disposed between the cathode chamber portion and the anode chamber portion to channel electrolytic gases generated in the cathode chamber portion to the anode chamber portion.

8. The electroosmotic pump system of claim 7 further comprising a mesh structure to support the additional gas permeable membrane.

9. The electroosmotic pump system of claim 1 wherein the gas-permeable membrane is disposed in a wall of the cathode chamber portion in proximity to the fluid outlet.

10. The electroosmotic pump system of claim 1 wherein the anode and cathode are inert electrodes fabricated from any one of platinum or graphite material.

11. The electroosmotic pump system of claim 1 further comprising a vent disposed adjacent to the fluid chamber and in proximity to the gas permeable membrane, with the catalyst disposed within the vent.

12. The electroosmotic pump system of claim 11 wherein the gas permeable membrane is disposed at an entrance to the vent.

13. The electroosmotic pump system of claim 11 wherein a vapor product formed at the catalyst is vented to ambient.

14. The electroosmotic pump system of claim 1 wherein the catalyst is fabricated from platinum.

15. The electroosmotic pump system of claim 1 wherein the catalyst is thermally insulated.

16. The electroosmotic pump system of claim 1 further comprising a heating element disposed in proximity to the catalyst.

17. A sealed electroosmotic pump system that pumps a fluid having a liquid phase through a closed loop upon application of an electric field, comprising:

a fluid chamber having a fluid inlet and a fluid outlet;

an anode disposed within an anode chamber portion;

a cathode disposed within a cathode chamber portion;

a structure that provides electroosmotic pumping upon application of the electric field between the anode and cathode, the structure creating a partition in the fluid chamber between the anode chamber portion and the cathode chamber portion;

a gas permeable membrane to remove electrolytic gases generated within the fluid chamber, the gas permeable membrane disposed in a wall of the fluid chamber; and

an osmotic membrane disposed in a wall of the fluid chamber to transport fluid in liquid phase back into the fluid chamber.

18. The sealed electroosmotic pump system of claim 17 further comprising a secondary loop disposed adjacent to a pair of openings in the cathode chamber portion.

19. The sealed electroosmotic pump system of claim 18 wherein the gas permeable membrane is disposed at the entrance to the secondary loop.

20. The sealed electroosmotic pump system of claim 18 further comprising a catalyst disposed within the secondary loop.

21. The sealed electroosmotic pump system of claim 20 wherein the catalyst combines the electrolytic gases to form a vapor product.

22. The sealed electroosmotic pump system of claim 17 wherein the electrolytic gases removed from the fluid chamber are hydrogen and oxygen.

23. The sealed electroosmotic pump system of claim 21 wherein the vapor product formed is water vapor.

24. The sealed electroosmotic pump system of claim 23 wherein the water vapor is condensed into water in the secondary loop downstream of the catalyst.

25. The sealed electroosmotic pump system of claim 17 further comprising an additional gas permeable membrane disposed between the cathode chamber portion and the anode chamber portion to channel electrolytic gases generated in the cathode chamber portion to the anode chamber portion.

26. The sealed electroosmotic pump system of claim 25 further comprising a mesh structure to support the additional gas permeable membrane.

27. The sealed electroosmotic pump system of claim 18 wherein the osmotic membrane is disposed at an exit from the secondary loop.

28. The sealed electroosmotic pump system of claim 27 wherein the osmotic membrane transports fluid in liquid phase from the secondary loop to the fluid chamber where it recombines with the fluid in the chamber.

29. The sealed electroosmotic pump system of claim 20 further comprising a heater disposed in proximity to the catalyst to keep the catalyst dry.

30. The sealed electroosmotic pump system of claim 20 further comprising an additional gas permeable membrane disposed in the secondary loop immediately downstream of the catalyst to prevent fluid in liquid phase from flowing back to the catalyst.

31. An electroosmotic pump system that pumps a working fluid having a liquid phase through a closed loop upon application of an electric field, comprising:

a fluid chamber having a fluid inlet and a fluid outlet;

a pumping structure rigidly fixed within the fluid chamber and partitioning the fluid chamber into two sides, the pumping structure providing electroosmotic pumping upon application of the electric field;

a pair of electrodes with one electrode disposed in each side of the fluid chamber, the electrodes providing the electric field across the pumping structure;

a gas permeable membrane disposed in a wall of the fluid chamber and providing for venting of electrolytic gases generated within the fluid chamber; and

a catalyst for recombining at least part of the electrolytic gases.

32. The electroosmotic pump system of claim 31 wherein the gas permeable membrane vents electrolytic gases to an environment in which the pump operates.

33. The electroosmotic pump system of claim 31 wherein the gas permeable membrane vents electrolytic gases to ambient.

34. The electroosmotic pump system of claim 31 further comprising an additional gas permeable membrane disposed between the two sides of the fluid chamber to channel electrolytic gases generated on an outlet side to an inlet side by supporting a pressure differential between the two sides.

35. The electroosmotic pump system of claim 34 further comprising a mesh structure to support the additional gas permeable membrane.

36. The electroosmotic pump system of claim 31 wherein the gas permeable membrane is disposed in a wall of the fluid chamber and located above the fluid inlet.

37. The electroosmotic pump system of claim 31 wherein the gas permeable membrane is disposed in a wall of the fluid chamber and located in proximity to the fluid outlet.

38. The electroosmotic pump system of claim 31 further comprising a vent disposed adjacent to the fluid chamber and in proximity to the gas permeable membrane, with the catalyst disposed within the vent.

39. The electroosmotic pump system of claim 38 wherein the gas permeable membrane is disposed at an entrance to the vent.

40. A sealed electroosmotic pump system that pumps a working fluid having a liquid phase through a closed loop upon application of an electric field, comprising:

a fluid chamber having a fluid inlet and a fluid outlet;

a pumping structure rigidly fixed within the fluid chamber and partitioning the fluid chamber into two sides, the pumping structure providing electroosmotic pumping upon application of the electric field;

a pair of electrodes with one electrode disposed in each side of the fluid chamber, the electrodes providing the electric field across the pumping structure;

a gas permeable membrane disposed in a wall of the fluid chamber and providing for removal of electrolytic gases generated within the fluid chamber; and

an osmotic membrane disposed in a wall of the fluid chamber to transport fluid in liquid phase back into the fluid chamber.

41. The sealed electroosmotic pump system of claim 40 further comprising a secondary loop disposed adjacent to a pair of openings in an inlet side of the fluid chamber.

42. The sealed electroosmotic pump system of claim 41 wherein the gas permeable membrane is disposed at an entrance to the secondary loop.

43. The sealed electroosmotic pump system of claim 41 further comprising a catalyst disposed within the secondary loop.

44. The sealed electroosmotic pump system of claim 43 wherein the catalyst combines the electrolytic gases to form a vapor product.

45. The sealed electroosmotic pump system of claim 40 wherein the electrolytic gases removed from the fluid chamber are hydrogen and oxygen.

46. The sealed electroosmotic pump system of claim 44 wherein the vapor product formed is water vapor.

47. The sealed electroosmotic pump system of claim 46 wherein the water vapor is condensed into water in the secondary loop downstream of the catalyst.

48. The sealed electroosmotic pump system of claim 40 further comprising an additional gas permeable membrane disposed between the two sides of the fluid chamber to channel electrolytic gases generated on an outlet side to an inlet side by supporting a pressure differential between the two sides.

49. The sealed electroosmotic pump system of claim 48 further comprising a mesh structure to support the additional gas permeable membrane.

50. The sealed electroosmotic pump system of claim 41 wherein the osmotic membrane is disposed at an exit from the secondary loop.

51. The sealed electroosmotic pump system of claim 50 wherein the osmotic membrane transports fluid in liquid phase from the secondary loop to the fluid chamber where it recombines with the working fluid.

52. The sealed electroosmotic pump system of claim 43 further comprising a heater disposed in proximity to the catalyst to keep the catalyst dry.

53. The sealed electroosmotic pump system of claim 43 further comprising an additional gas permeable membrane disposed in the secondary loop immediately downstream of the catalyst to prevent fluid in liquid phase from flowing back to the catalyst.

54. A method for controlling electrolysis gases generated in a closed-loop electroosmotic pump system that pumps fluid having a liquid phase through a fluid chamber from an inlet to an outlet, the fluid chamber having a pumping structure that partitions the fluid chamber into separate portions, and a plurality of gas permeable membranes, the method comprising the steps of:

applying an electric field between a pair of electrodes disposed in the separate portions of the fluid chamber;

drawing the fluid in liquid phase through the pumping structure from an inlet region to an outlet region of the fluid chamber upon application of the electric field between the pair of electrodes;

venting electrolysis gases that are generated within the separate portions of the fluid chamber through a first gas permeable membrane disposed in a wall of the fluid chamber; and

recombining at least part of the electrolysis gases.

55. The method for controlling electrolysis gases of claim 54 wherein the venting of electrolysis gases occurs through a vent disposed adjacent to the first gas permeable membrane.

56. The method for controlling electrolysis gases of claim 54 wherein the gas-permeable membrane vents the electrolysis gases to ambient.

57. The method for controlling electrolysis gases of claim 54 wherein the electrolysis gases vented are hydrogen and oxygen.

58. The method for controlling electrolysis gases of claim 54 further comprising the step of channeling electrolysis gases generated in a downstream portion of the fluid chamber to an upstream portion of the fluid chamber through a second gas permeable membrane disposed between the separate portions.

59. The method for controlling electrolysis gases of claim 54 further comprising the step of venting a vapor product to ambient.

60. The method for controlling electrolysis gases of claim 55 further comprising the step of positioning a catalyst in the vent and in proximity to the first gas permeable membrane.

61. The method for controlling electrolysis gases of claim 60 further comprising the step of thermally insulating the catalyst.

62. The method for controlling electrolysis gases of claim 60 further comprising the step of disposing a heating element in proximity to the catalyst.

63. A method for controlling electrolysis gases generated in a sealed closed-loop electroosmotic pump system that pumps fluid having a liquid phase through a fluid chamber from an inlet to an outlet, the fluid chamber having a pumping structure that partitions the fluid chamber into separate portions, and a plurality of gas permeable membranes and an osmotic membrane, the electroosmotic pump system having a catalyst and an additional gas permeable membrane disposed in a secondary loop adjacent the fluid chamber, the method comprising the steps of:

applying an electric field between a pair of electrodes disposed in the separate portions of the fluid chamber;

drawing the fluid in liquid phase through the pumping structure from an inlet region to an outlet region of the fluid chamber upon application of the electric field between the pair of electrodes; and

removing electrolysis gases that are generated within the separate portions of the fluid chamber through a first gas permeable membrane disposed in a wall of the fluid chamber;

recombining the electrolysis gases in the catalyst to form a vapor product;

condensing the vapor product to fluid in liquid phase; and

pumping the fluid in liquid phase through the osmotic membrane to the inlet region of the fluid chamber.

64. The method for controlling electrolysis gases of claim 63 further comprising the step of channeling electrolysis gases generated in a downstream portion of the fluid chamber to an upstream portion of the fluid chamber through a second gas permeable membrane disposed between the separate portions.

65. The method for controlling electrolysis gases of claim 63 wherein the electrolysis gases removed from the fluid chamber are oxygen and hydrogen.

66. The method for controlling electrolysis gases of claim 63 wherein the vapor product formed is water vapor.

67. The method for controlling electrolysis gases of claim 63 wherein the condensed vapor product is water.

68. The method for controlling electrolysis gases of claim 63 further comprising the step of disposing the first gas permeable membrane adjacent to an entrance to the secondary loop.

69. The method for controlling electrolysis gases of claim 63 further comprising the step of disposing the additional gas permeable membrane in the secondary loop immediately downstream of the catalyst to prevent the fluid in liquid phase from flowing back to the catalyst.

70. The method for controlling electrolysis gases of claim 63 further comprising the step of disposing the osmotic membrane adjacent to an exit from the secondary loop.

71. The method for controlling electrolysis gases of claim 63 further comprising the step of disposing a heater in proximity to the catalyst to keep the catalyst dry.