U.S. patent application number 10/769715 was filed with the patent office on 2004-11-25 for method and apparatus for low-cost electrokinetic pump manufacturing.
Invention is credited to Cichocki, Zbigniew, Kenny, Thomas W., Lin, Tien-Chih Eric, Lovette, James, Munch, Mark, Shook, James Gill, Werner, Douglas, Zeng, Shulin.
Application Number | 20040234378 10/769715 |
Document ID | / |
Family ID | 32927455 |
Filed Date | 2004-11-25 |
United States Patent
Application |
20040234378 |
Kind Code |
A1 |
Lovette, James ; et
al. |
November 25, 2004 |
Method and apparatus for low-cost electrokinetic pump
manufacturing
Abstract
An electroosmotic pump used in a closed loop cooling system. The
pump includes a fluid chamber, a pumping element, an inlet
electrode, an outlet electrode, and means for providing electrical
voltage to the inlet electrode and the outlet electrode to produce
an electrical field therebetween. The pumping element is configured
to pump fluid therethrough, and the pumping element is positioned
to segment the fluid chamber into an inlet chamber including a
fluid inlet port and an outlet chamber including a fluid outlet
port. The size of the inlet chamber is proportional to a
predetermined residence time of the inlet chamber. The inlet
electrode is positioned within the inlet chamber and a
predetermined distance from a first surface of the pumping element.
The outlet electrode is positioned within the outlet chamber and a
predetermined distance from a second surface of the pumping
element.
Inventors: |
Lovette, James; (San
Francisco, CA) ; Munch, Mark; (Los Altos Hills,
CA) ; Shook, James Gill; (Santa Cruz, CA) ;
Zeng, Shulin; (Los Altos, CA) ; Kenny, Thomas W.;
(San Carlos, CA) ; Werner, Douglas; (Atherton,
CA) ; Cichocki, Zbigniew; (Newark, CA) ; Lin,
Tien-Chih Eric; (Fremont, CA) |
Correspondence
Address: |
HAVERSTOCK & OWENS LLP
162 NORTH WOLFE ROAD
SUNNYVALE
CA
94086
US
|
Family ID: |
32927455 |
Appl. No.: |
10/769715 |
Filed: |
January 29, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60444269 |
Jan 31, 2003 |
|
|
|
Current U.S.
Class: |
417/48 ;
257/E23.098 |
Current CPC
Class: |
F28F 19/006 20130101;
H01L 2924/09701 20130101; H01L 2924/0002 20130101; H01L 2924/0002
20130101; F04B 17/00 20130101; F28D 15/0266 20130101; H01L 23/473
20130101; H01L 2924/00 20130101 |
Class at
Publication: |
417/048 |
International
Class: |
F04F 011/00 |
Claims
What is claimed is:
1. An electroosmotic pump comprising: a. a fluid chamber; b. a
pumping element for pumping fluid therethrough, the pumping element
positioned to segment the fluid chamber into an inlet chamber
including a fluid inlet port and an outlet chamber including a
fluid outlet port; c. an inlet electrode positioned within the
inlet chamber and a predetermined distance from a first surface of
the pumping element; d. an outlet electrode positioned within the
outlet chamber; and e. means for providing electrical voltage to
the inlet electrode and the outlet electrode to produce an
electrical field therebetween, wherein the means for providing is
coupled to the inlet electrode and the outlet electrode.
2. The electroosmotic pump according to claim 1 wherein the
predetermined distance that the inlet electrode is positioned from
the first surface is in a range of about 0.05 mm to about 5.0
mm.
3. The electroosmotic pump according to claim 1 wherein the outlet
electrode is positioned a predetermined distance from a second
surface of the pumping element.
4. The electroosmotic pump according to claim 3 wherein the
predetermined distance that the outlet electrode is positioned from
the second surface is in a range of about 0.05 mm to about 5.0
mm.
5. The electroosmotic pump according to claim 1 wherein the outlet
electrode is positioned on a second surface of the pumping
element.
6. The electroosmotic pump according to claim 1 wherein a residence
time of the inlet chamber is in a range of about {fraction (1/20)}
of a minute to about 1 minute.
7. The electroosmotic pump according to claim 6 wherein a volume of
the inlet chamber is equal to an area of the pumping element
multiplied by a width of between about 0.4 cm and about 3.0 cm.
8. The electroosmotic pump according to claim 1 wherein the
electroosmotic pump is manufactured using one or more materials
comprising metal, glass, ceramic, plastic, or a combination
thereof.
9. The electroosmotic pump according to claim 8 wherein the one or
more materials are coupled by one or more sealing materials.
10. The electroosmotic pump according to claim 8 wherein the one or
more sealing materials comprise solder, sealing glass, low modulus
adhesives, or a combination thereof.
11. The electroosmotic pump according to claim 10 wherein low
modulus adhesives seal the pumping element to a housing of the
electroosmotic pump.
12. The electroosmotic pump according to claim 1 wherein the
electroosmotic pump is manufactured using one or more pump
materials such that each pump material is compatible with the
fluid, or such that the one or more pump materials that are not
compatible with the fluid are overcoated with a compatible
material.
13. The electroosmotic pump according to claim 12 wherein the fluid
comprises a buffered water solution.
14. The electroosmotic pump according to claim 13 wherein the one
or more pump materials comprise insulating materials that are
compatible with buffered water solutions.
15. The electroosmotic pump according to claim 14 wherein the pump
material is selected from a group consisting of silicon nitride,
titania, alumina, silica, borosilicate, vycor, and plastic.
16. The electroosmotic pump according to claim 1 wherein the
pumping element exhibits a negative zeta potential in the presence
of the fluid and the inlet electrode is an anode electrode and the
outlet electrode is a cathode electrode.
17. The electroosmotic pump according to claim 16 wherein a
material of the anode electrode is selected from the group
consisting of platinum, platinum clad niobium, platinum plated
titanium, platinum clad tantalum, graphite, glassy carbon, mixed
metal oxide coating on titanium, silver-impregnated ink, and
dimensionally-stable anode material.
18. The electroosmotic pump according to claim 17 wherein the mixed
metal oxide coating on titanium includes an iridium and tantalum
oxide coating on titanium.
19. The electroosmotic pump according to claim 17 wherein the
dimensionally-stable anode material includes one from the group
consisting of conducting iridium oxide coating on titanium and
ruthenium oxide coating on titanium
20. The electroosmotic pump according to claim 16 wherein a
material of the cathode electrode is selected from a group
consisting of platinum, copper, platinum plated titanium, stainless
steel, graphite, gold, plated silver, silver-impregnated ink, and
glassy carbon.
21. The electroosmotic pump according to claim 1 wherein the
pumping element exhibits a positive zeta potential in the presence
of the fluid and the inlet electrode is a cathode electrode and the
outlet electrode is an anode electrode.
22. The electroosmotic pump according to claim 21 wherein a
material of the anode electrode is selected from the group
consisting of platinum, platinum clad niobium, platinum plated
titanium, platinum clad tantalum, graphite, glassy carbon, mixed
metal oxide coating on titanium, silver-impregnated ink, and
dimensionally-stable anode material.
23. The electroosmotic pump according to claim 22 wherein the mixed
metal oxide coating on titanium includes an iridium and tantalum
oxide coating on titanium.
24. The electroosmotic pump according to claim 22 wherein the
dimensionally-stable anode material includes one from the group
consisting of conducting iridium oxide coating on titanium and
ruthenium oxide coating on titanium
25. The electroosmotic pump according to claim 21 wherein a
material of the cathode electrode is selected from a group
consisting of platinum, copper, platinum plated titanium, stainless
steel, graphite, gold, plated silver, silver-impregnated ink, and
glassy carbon.
26. The electroosmotic pump according to claim 1 further comprising
one or more inlet chambers, one or more pumping elements, and one
or more outlet chambers, wherein each inlet chamber includes one or
more fluid inlet ports.
27. The electroosmotic pump according to claim 1 further comprising
a recombination chamber coupled to the inlet chamber to recombine
an inlet chamber gas and an outlet chamber gas.
28. The electroosmotic pump according to claim 1 wherein the inlet
port to the inlet chamber is configured and positioned such that
fluid entering the inlet chamber becomes well mixed.
29. The electroosmotic pump according to claim 28 wherein the fluid
is well mixed by providing the fluid from the inlet port into the
inlet chamber at a high average velocity.
30. The electroosmotic pump according to claim 29 wherein the high
average velocity of the fluid entering the inlet chamber at the
inlet port is greater than about 25 centimeters per second.
31. An electroosmotic pump comprising: a. a fluid chamber; b. a
pumping element for pumping fluid therethrough, the pumping element
positioned to segment the fluid chamber into an inlet chamber
including a fluid inlet port and an outlet chamber including a
fluid outlet port, wherein a size of the inlet chamber is
proportional to a predetermined residence time of the inlet
chamber; c. an inlet electrode positioned within the inlet chamber;
d. an outlet electrode positioned within the outlet chamber; and e.
means for providing electrical voltage to the inlet electrode and
the outlet electrode to produce an electrical field therebetween,
wherein the means for providing is coupled to the inlet electrode
and the outlet electrode.
32. The electroosmotic pump according to claim 31 wherein the
residence time of the inlet chamber is in a range of about
{fraction (1/20)} of a minute to about 1 minute.
33. The electroosmotic pump according to claim 32 wherein a volume
of the inlet chamber is equal to an area of the pumping element
multiplied by a width of between about 0.4 cm and about 3.0 cm.
34. The electroosmotic pump according to claim 31 wherein the inlet
electrode is positioned a predetermined distance from a first
surface of the pumping element.
35. The electroosmotic pump according to claim 34 wherein the
predetermined distance that the inlet electrode is positioned from
the first surface is in a range of about 0.05 mm to about 5.0
mm.
36. The electroosmotic pump according to claim 31 wherein the
outlet electrode is positioned a predetermined distance from a
second surface of the pumping element.
37. The electroosmotic pump according to claim 36 wherein the
predetermined distance that the outlet electrode is positioned from
the second surface is in a range of about 0.05 mm to about 5.0
mm.
38. The electroosmotic pump according to claim 31 wherein the
outlet electrode is positioned on a second surface of the pumping
element.
39. The electroosmotic pump according to claim 31 consisting of one
or more materials that are non-reactive to oxygen.
40. The electroosmotic pump according to claim 31 wherein the
electroosmotic pump is manufactured using one or more materials
comprising metal, glass, ceramic, plastic, or a combination
thereof.
41. The electroosmotic pump according to claim 40 wherein the one
or more materials are coupled by one or more sealing materials.
42. The electroosmotic pump according to claim 41 wherein the one
or more sealing materials comprise solder, sealing glass, low
modulus adhesives, or a combination thereof.
43. The electroosmotic pump according to claim 42 wherein low
modulus adhesives seal the pumping element to a housing of the
electroosmotic pump.
44. The electroosmotic pump according to claim 31 wherein the
electroosmotic pump is manufactured using one or more pump
materials such that each pump material is compatible with the
fluid, or such that the one or more pump materials that are not
compatible with the fluid are overcoated with a compatible
material.
45. The electroosmotic pump according to claim 44 wherein the fluid
comprises a buffered water solution.
46. The electroosmotic pump according to claim 45 wherein the one
or more pump materials comprise insulating materials that are
compatible with buffered water solutions.
47. The electroosmotic pump according to claim 46 wherein the pump
material is selected from a group consisting of silicon nitride,
titania, alumina, silica, borosilicate, vycor, and plastic.
48. The electroosmotic pump according to claim 31 wherein the
pumping element exhibits a negative zeta potential in the presence
of the fluid and the inlet electrode is an anode electrode and the
outlet electrode is a cathode electrode.
49. The electroosmotic pump according to claim 48 wherein a
material of the anode electrode is selected from the group
consisting of platinum, platinum clad niobium, platinum plated
titanium, platinum clad tantalum, graphite, glassy carbon, mixed
metal oxide coating on titanium, silver-impregnated ink, and
dimensionally-stable anode material.
50. The electroosmotic pump according to claim 49 wherein the mixed
metal oxide coating on titanium includes an iridium and tantalum
oxide coating on titanium.
51. The electroosmotic pump according to claim 49 wherein the
dimensionally-stable anode material includes one from the group
consisting of conducting iridium oxide coating on titanium and
ruthenium oxide coating on titanium.
52. The electroosmotic pump according to claim 48 wherein a
material of the cathode electrode is selected from a group
consisting of platinum, copper, platinum plated titanium, stainless
steel, graphite, gold, plated silver, silver-impregnated ink, and
glassy carbon.
53. The electroosmotic pump according to claim 31 wherein the
pumping element exhibits a positive zeta potential in the presence
of the fluid and the inlet electrode is a cathode electrode and the
outlet electrode is an anode electrode.
54. The electroosmotic pump according to claim 53 wherein a
material of the anode electrode is selected from the group
consisting of platinum, platinum clad niobium, platinum plated
titanium, platinum clad tantalum, graphite, glassy carbon, mixed
metal oxide coating on titanium, silver-impregnated ink, and
dimensionally-stable anode material.
55. The electroosmotic pump according to claim 54 wherein the mixed
metal oxide coating on titanium includes an iridium and tantalum
oxide coating on titanium.
56. The electroosmotic pump according to claim 54 wherein the
dimensionally-stable anode material includes one from the group
consisting of conducting iridium oxide coating on titanium and
ruthenium oxide coating on titanium.
57. The electroosmotic pump according to claim 53 wherein a
material of the cathode electrode is selected from a group
consisting of platinum, copper, platinum plated titanium, stainless
steel, graphite, gold, plated silver, silver-impregnated ink, and
glassy carbon.
58. The electroosmotic pump according to claim 31 further
comprising one or more inlet chambers, one or more pumping
elements, and one or more outlet chambers, wherein each inlet
chamber includes one or more fluid inlet ports.
59. The electroosmotic pump according to claim 31 further
comprising a recombination chamber coupled to the inlet chamber to
recombine an inlet chamber gas and an outlet chamber gas.
60. The electroosmotic pump according to claim 31 wherein the inlet
port to the inlet chamber is configured and positioned such that
fluid entering the inlet chamber becomes well mixed.
61. The electroosmotic pump according to claim 60 wherein the fluid
is well mixed by providing the fluid from the inlet port into the
inlet chamber at a high average velocity.
62. The electroosmotic pump according to claim 61 wherein the high
average velocity of the fluid entering the inlet chamber at the
inlet port is greater than about 25 centimeters per second.
63. An electroosmotic pump comprising: a. a fluid chamber; b. a
pumping element for pumping fluid therethrough, the pumping element
positioned to segment the fluid chamber into an inlet chamber
including a fluid inlet port and an outlet chamber including a
fluid outlet port; c. a gas permeable element to allow passage of a
gas from the outlet chamber to the inlet chamber while preventing
the passage of the fluid therethrough; d. an inlet electrode
positioned within the inlet chamber and a predetermined distance
from a first surface of the pumping element; e. an outlet electrode
positioned within the outlet chamber; and f. means for providing
electrical voltage to the inlet electrode and the outlet electrode
to produce an electrical field therebetween, wherein the means for
providing is coupled to the inlet electrode and the outlet
electrode.
64. The electroosmotic pump according to claim 63 wherein the gas
permeable element allows the passage of an outlet chamber gas from
the outlet chamber to the inlet chamber.
65. The electroosmotic pump according to claim 64 wherein the
outlet chamber gas is predominately hydrogen.
66. The electroosmotic pump according to claim 64 wherein the
outlet chamber gas is predominately oxygen.
67. The electroosmotic pump according to claim 63 wherein the
predetermined distance that the inlet electrode is positioned from
the first surface is in a range of about 0.05 mm to about 5.0
mm.
68. The electroosmotic pump according to claim 63 wherein the
outlet electrode is positioned a predetermined distance from a
second surface of the pumping element.
69. The electroosmotic pump according to claim 68 wherein the
predetermined distance that the outlet electrode is positioned from
the second surface is in a range of about 0.05 mm to about 5.0
mm.
70. The electroosmotic pump according to claim 63 wherein the
outlet electrode is positioned on a second surface of the pumping
element.
71. The electroosmotic pump according to claim 63 wherein a
residence time of the inlet chamber is in a range of about
{fraction (1/20)} of a minute to about 1 minute.
72. The electroosmotic pump according to claim 63 wherein a volume
of the inlet chamber is equal to an area of the pumping element
multiplied by a width of between about 0.4 cm and about 3.0 cm.
73. The electroosmotic pump according to claim 63 wherein the
electroosmotic pump is manufactured using one or more materials
comprising metal, glass, ceramic, plastic, or a combination
thereof.
74. The electroosmotic pump according to claim 73 wherein the one
or more materials are coupled by one or more sealing materials.
75. The electroosmotic pump according to claim 74 wherein the one
or more sealing materials comprise solder, sealing glass, low
modulus adhesives, or a combination thereof.
76. The electroosmotic pump according to claim 75 wherein low
modulus adhesives seal the pumping element to a housing of the
electroosmotic pump.
77. The electroosmotic pump according to claim 63 wherein the
electroosmotic pump is manufactured using one or more pump
materials such that each pump material is compatible with the
fluid, or such that the one or more pump materials that are not
compatible with the fluid are overcoated with a compatible
material.
78. The electroosmotic pump according to claim 77 wherein the fluid
comprises a buffered water solution.
79. The electroosmotic pump according to claim 78 wherein the one
or more pump materials comprise insulating materials that are
compatible with buffered water solutions.
80. The electroosmotic pump according to claim 79 wherein the pump
material is selected from a group consisting of silicon nitride,
titania, alumina, silica, borosilicate, vycor, and plastic.
81. The electroosmotic pump according to claim 63 wherein the
pumping element exhibits a negative zeta potential in the presence
of the fluid and the inlet electrode is an anode electrode and the
outlet electrode is a cathode electrode.
82. The electroosmotic pump according to claim 81 wherein a
material of the anode electrode is selected from the group
consisting of platinum, platinum clad niobium, platinum plated
titanium, platinum clad tantalum, graphite, glassy carbon, mixed
metal oxide coating on titanium, silver-impregnated ink, and
dimensionally-stable anode material.
83. The electroosmotic pump according to claim 82 wherein the mixed
metal oxide coating on titanium includes an iridium and tantalum
oxide coating on titanium.
84. The electroosmotic pump according to claim 82 wherein the
dimensionally-stable anode material includes one from the group
consisting of conducting iridium oxide coating on titanium and
ruthenium oxide coating on titanium
85. The electroosmotic pump according to claim 81 wherein a
material of the cathode electrode is selected from a group
consisting of platinum, copper, platinum plated titanium, stainless
steel, graphite, gold, plated silver, silver-impregnated ink, and
glassy carbon.
86. The electroosmotic pump according to claim 63 wherein the
pumping element exhibits a positive zeta potential in the presence
of the fluid and the inlet electrode is a cathode electrode and the
outlet electrode is an anode electrode.
87. The electroosmotic pump according to claim 86 wherein a
material of the anode electrode is selected from the group
consisting of platinum, platinum clad niobium, platinum plated
titanium, platinum clad tantalum, graphite, glassy carbon, mixed
metal oxide coating on titanium, silver-impregnated ink, and
dimensionally-stable anode material.
88. The electroosmotic pump according to claim 87 wherein the mixed
metal oxide coating on titanium includes an iridium and tantalum
oxide coating on titanium.
89. The electroosmotic pump according to claim 87 wherein the
dimensionally-stable anode material includes one from the group
consisting of conducting iridium oxide coating on titanium and
ruthenium oxide coating on titanium
90. The electroosmotic pump according to claim 86 wherein a
material of the cathode electrode is selected from a group
consisting of platinum, copper, platinum plated titanium, stainless
steel, graphite, gold, plated silver, silver-impregnated ink, and
glassy carbon.
91. The electroosmotic pump according to claim 63 further
comprising one or more inlet chambers, one or more pumping
elements, and one or more outlet chambers, wherein each inlet
chamber includes one or more fluid inlet ports.
92. The electroosmotic pump according to claim 63 further
comprising a recombination chamber coupled to the inlet chamber to
recombine an inlet chamber gas and an outlet chamber gas.
93. The electroosmotic pump according to claim 63 wherein the inlet
port to the inlet chamber is configured and positioned such that
fluid entering the inlet chamber becomes well mixed.
94. The electroosmotic pump according to claim 93 wherein the fluid
is well mixed by providing the fluid from the inlet port into the
inlet chamber at a high average velocity.
95. The electroosmotic pump according to claim 94 wherein the high
average velocity of the fluid entering the inlet chamber at the
inlet port is greater than about 25 centimeters per second.
96. A pump assembly comprising: a. a structure adapted to house a
pumping element; b. a plurality of fluid lines coupled to the
structure; and c. a ductile material configured between the
structure and each fluid line, wherein the ductile material has a
thermal expansion characteristic substantially similar with a
structure material.
97. The pump assembly according to claim 96 wherein the structure
further comprises a first electrical port configured to provide a
first electrical contact to a first side of the pumping
element.
98. The pump assembly according to claim 97 further comprising the
ductile material positioned between the first electrical contact
and the first electrical port.
99. The pump assembly according to claim 97 further comprising: a.
an adhesive material for coupling the first electrical contact to
the first side; and b. a passivation layer applied to the adhesive
material, wherein the passivation layer protects the adhesive
material from migration.
100. The pump assembly according to claim 96 wherein a substantial
portion of the pumping element includes non-parallel apertures.
101. The pump assembly according to claim 100 further comprises an
epoxy material applied to a perimeter surface of the pumping
element, wherein the epoxy has an expansion characteristic matching
a pumping element material.
102. The pump assembly according to claim 97 wherein the structure
further comprises a second electrical port configured to provide a
second electrical contact to the second side.
103. The pump assembly according to claim 102 further comprising
the ductile material positioned between the second electrical
contact and the second electrical port.
104. The pump assembly according to claim 102 wherein the first
electrical port and the second electrical port are configured on a
same outer surface plane of the structure.
105. The pump assembly according to claim 102 wherein the first
electrical port and the second electrical port are configured on a
different outer surface plane of the structure.
106. The pump assembly according to claim 96 wherein the pumping
element further comprises a first side and a second side, wherein
the first side is associated with a fluid inlet area in the
structure and the second side is associated with a fluid outlet
area in the structure, the plurality of fluid lines for circulating
fluid from the fluid inlet area to the fluid outlet area.
107. The pump assembly according to claim 96 wherein the structure
further comprises a first outer surface and a second outer surface,
wherein a first fluid line and a second fluid line of the plurality
of fluid lines are coupled to the structure on the first outer
surface.
108. The pump assembly according to claim 96 wherein the structure
further comprises a first outer surface and a second outer surface,
wherein a first fluid lie of the plurality of fluid lines is
coupled to the first outer surface and a second fluid line of the
plurality of fluid lines is coupled to the second outer
surface.
109. The pump assembly according to claim 106 wherein the structure
further comprises: a. a base having a receptacle for holding the
pumping element wherein a first fluid line is in communication with
the fluid inlet area and a second fluid line is in communication
with the fluid outlet area; and b. a lid coupled to the base and
configured to provide a sealed engagement thereto.
110. The pump assembly according to claim 109 wherein the base
further comprises a cavity for recombining excess hydrogen and
oxygen gases into water.
111. The pump assembly according to claim 96 wherein the ductile
material is Tungsten.
112. The pump assembly according to claim 96 wherein the pumping
element is made of borosilicate glass.
113. The pump assembly according to claim 96 wherein the fluid
lines are made of Copper.
114. The pump assembly according to claim 102 wherein the first and
second electrical contacts are made of Copper.
115. The pump assembly according to claim 102 wherein the first and
second electrical contacts are made of Tungsten.
116. A closed loop system for cooling a circuit comprising: a. at
least one heat exchanger in contact with the circuit having a
plurality of heat exchange fluid ports coupled to one or more fluid
lines for cooling the circuit; and b. at least one pump assembly
coupled to the heat exchanger comprising: i. a structure adapted to
house a pumping element, the structure having a plurality of pump
fluid ports coupled to the fluid lines; and ii. a ductile material
configured between the pump fluid ports and each corresponding
fluid line, wherein the ductile material has a thermal expansion
characteristic substantially similar with a structure material.
117. The closed loop system according to claim 116 further
comprising at least one heat rejecter having a plurality of heat
rejecter fluid ports coupled to the fluid lines.
118. The closed loop system according to claim 117 wherein the
ductile material is configured between the plurality of fluid lines
and the heat rejecter fluid ports, the ductile material for sealing
the heat rejecter.
119. The closed loop system according to claim 116 wherein the
ductile material is configured between the plurality of fluid lines
and the heat exchanger fluid ports, the ductile material for
sealing the heat exchanger.
Description
RELATED APPLICATIONS
[0001] This Patent Application claims priority under 35 U.S.C. 119
(e) of the co-pending U.S. Provisional Patent Application, Ser. No.
60/444,269, filed Jan. 31, 2003 and entitled "REMEDIES FOR FREEZING
IN CLOSED-LOOP LIQUID COOLING FOR ELECTRONIC DEVICES". The
co-pending U.S. Provisional Patent Application Ser. No. 60/444,269,
filed Jan. 31, 2003 and entitled "REMEDIES FOR FREEZING IN
CLOSED-LOOP LIQUID COOLING FOR ELECTRONIC DEVICES" is hereby
incorporated by reference.
FIELD OF THE INVENTION
[0002] The invention relates to a method and apparatus for cooling
a heat producing device in general, and specifically, to a
cost-effective electrokinetic pump assembly and method of
manufacturing thereof.
BACKGROUND OF THE INVENTION
[0003] Electrokinetic pumps are capable of generating flowrates in
excess of 100 mL/min and pressures in excess of 10 PSI. As known in
the art, electrokinetic pumps operate by applying a voltage to
electrodes positioned on opposite sides of a porous pumping element
within a housing. Prior art electrokinetic pumps are contained
within housings, some of which have design disadvantages. These
disadvantages impair consistent performance of the pump as well as
diminish the reliability of the pump. In particular, the different
thermal expansion coefficients of the array of materials used in
existing electrokinetic pumps can cause leakage problems and
feedthrough failure. In addition, prior art electrokinetic pumps do
not take into consideration the mismatch of thermal expansion
between the material of the pump housing and the fluid ports as
well as fluid lines attached to the pump housing. Such a mismatch
in thermally expansive materials may cause leakage or breakage
between the pump and fluid lines. Prior art electrokinetic pump
housings which attempt to rectify these problems have complex
designs which makes manufacturing of the pump expensive, time
consuming and labor-intensive.
[0004] Further, physical design configurations of prior art
electrokinetic pumps does not promote optimal use. In particular,
specifications for fluid chamber sizes and positions of the pumping
elements, and their electrodes, can be improved to better optimize
the performance of the electrokinetic pump.
[0005] What is needed is a sealed pump housing having a design
configuration which rectifies these disadvantages and is
manufacturable in a cost effective manner.
SUMMARY OF THE INVENTION
[0006] One aspect of the present invention includes an
electroosmotic pump comprising a fluid chamber, a pumping element
for pumping fluid therethrough, the pumping element positioned to
segment the fluid chamber into an inlet chamber including a fluid
inlet port and an outlet chamber including a fluid outlet port, an
inlet electrode positioned within the inlet chamber and a
predetermined distance from a first surface of the pumping element,
an outlet electrode positioned within the outlet chamber, and means
for providing electrical voltage to the inlet electrode and the
outlet electrode to produce an electrical field therebetween,
wherein the means for providing is coupled to the inlet electrode
and the outlet electrode. The predetermined distance that the inlet
electrode is positioned from the first surface can be in a range of
about 0.05 mm to about 5.0 mm. The outlet electrode can be
positioned a predetermined distance from a second surface of the
pumping element. The predetermined distance that the outlet
electrode is positioned from the second surface can be in a range
of about 0.05 mm to about 5.0 mm. The outlet electrode can be
positioned on a second surface of the pumping element. A residence
time of the inlet chamber is in a range of about {fraction (1/20)}
of a minute to about 1 minute. A volume of the inlet chamber can be
equal to an area of the pumping element multiplied by a width of
between about 0.4 cm and about 3.0 cm. The electroosmotic pump can
be manufactured using one or more materials comprising metal,
glass, ceramic, plastic, or a combination thereof. The one or more
materials can be coupled by one or more sealing materials. The one
or more sealing materials can comprise solder, sealing glass, low
modulus adhesives, or a combination thereof. Low modulus adhesives
can seal the pumping element to a housing of the electroosmotic
pump. The electroosmotic pump can be manufactured using one or more
pump materials such that each pump material is compatible with the
fluid, or such that the one or more pump materials that are not
compatible with the fluid are overcoated with a compatible
material. The fluid can comprise a buffered water solution. The one
or more pump materials can comprise insulating materials that are
compatible with buffered water solutions. The pump material can be
selected from a group consisting of silicon nitride, titania,
alumina, silica, borosilicate, vycor, and plastic. The pumping
element can exhibit a negative zeta potential in the presence of
the fluid and the inlet electrode is an anode electrode and the
outlet electrode is a cathode electrode. The pumping element can
exhibit a positive zeta potential in the presence of the fluid and
the inlet electrode is a cathode electrode and the outlet electrode
is an anode electrode. A material of the anode electrode can be
selected from the group consisting of platinum, platinum clad
niobium, platinum plated titanium, platinum clad tantalum,
graphite, glassy carbon, mixed metal oxide coating on titanium,
silver-impregnated ink, and dimensionally-stable anode material.
The mixed metal oxide coating on titanium can include an iridium
and tantalum oxide coating on titanium. The dimensionally-stable
anode material can include one from the group consisting of
conducting iridium oxide coating on titanium and ruthenium oxide
coating on titanium. A material of the cathode electrode can be
selected from a group consisting of platinum, copper, platinum
plated titanium, stainless steel, graphite, gold, plated silver,
silver-impregnated ink, and glassy carbon. The electroosmotic pump
can include one or more inlet chambers, one or more pumping
elements, and one or more outlet chambers, wherein each inlet
chamber includes one or more fluid inlet ports. The electroosmotic
pump can also include a recombination chamber coupled to the inlet
chamber to recombine an inlet chamber gas and an outlet chamber
gas. The inlet port to the inlet chamber can be configured and
positioned such that fluid entering the inlet chamber becomes well
mixed. The fluid can be well mixed by providing the fluid from the
inlet port into the inlet chamber at a high average velocity. The
high average velocity of the fluid entering the inlet chamber at
the inlet port can be greater than about 25 centimeters per
second.
[0007] In another aspect of the present invention, an
electroosmotic pump comprises a fluid chamber, a pumping element
for pumping fluid therethrough, the pumping element positioned to
segment the fluid chamber into an inlet chamber including a fluid
inlet port and an outlet chamber including a fluid outlet port,
wherein a size of the inlet chamber is proportional to a
predetermined residence time of the inlet chamber, an inlet
electrode positioned within the inlet chamber, an outlet electrode
positioned within the outlet chamber, and means for providing
electrical voltage to the inlet electrode and the outlet electrode
to produce an electrical field therebetween, wherein the means for
providing is coupled to the inlet electrode and the outlet
electrode. The residence time of the inlet chamber can be in a
range of about {fraction (1/20)} of a minute to about 1 minute. A
volume of the inlet chamber can be equal to an area of the pumping
element multiplied by a width of between about 0.4 cm and about 3.0
cm. The inlet electrode can be positioned a predetermined distance
from a first surface of the pumping element. The predetermined
distance that the inlet electrode is positioned from the first
surface can be in a range of about 0.05 mm to about 5.0 mm. The
outlet electrode can be positioned a predetermined distance from a
second surface of the pumping element. The predetermined distance
that the outlet electrode is positioned from the second surface can
be in a range of about 0.05 mm to about 5.0 mm. The outlet
electrode can be positioned on a second surface of the pumping
element. The electroosmotic pump can consist of one or more
materials that are non-reactive to oxygen. The electroosmotic pump
can be manufactured using one or more materials comprising metal,
glass, ceramic, plastic, or a combination thereof. The one or more
materials can be coupled by one or more sealing materials. The one
or more sealing materials can comprise solder, sealing glass, low
modulus adhesives, or a combination thereof. Low modulus adhesives
can seal the pumping element to a housing of the electroosmotic
pump. The electroosmotic pump can be manufactured using one or more
pump materials such that each pump material is compatible with the
fluid, or such that the one or more pump materials that are not
compatible with the fluid are overcoated with a compatible
material. The fluid can comprise a buffered water solution. The one
or more pump materials can comprise insulating materials that are
compatible with buffered water solutions. The pump material can be
selected from a group consisting of silicon nitride, titania,
alumina, silica, borosilicate, vycor, and plastic. The pumping
element can exhibit a negative zeta potential in the presence of
the fluid and the inlet electrode is an anode electrode and the
outlet electrode is a cathode electrode. The pumping element can
exhibit a positive zeta potential in the presence of the fluid and
the inlet electrode is a cathode electrode and the outlet electrode
is an anode electrode. A material of the anode electrode can be
selected from the group consisting of platinum, platinum clad
niobium, platinum plated titanium, platinum clad tantalum,
graphite, glassy carbon, mixed metal oxide coating on titanium,
silver-impregnated ink, and dimensionally-stable anode material.
The mixed metal oxide coating on titanium can include an iridium
and tantalum oxide coating on titanium. The dimensionally-stable
anode material can include one from the group consisting of
conducting iridium oxide coating on titanium and ruthenium oxide
coating on titanium. A material of the cathode electrode can be
selected from a group consisting of platinum, copper, platinum
plated titanium, stainless steel, graphite, gold, plated silver,
silver-impregnated ink, and glassy carbon. The electroosmotic pump
can include one or more inlet chambers, one or more pumping
elements, and one or more outlet chambers, wherein each inlet
chamber includes one or more fluid inlet ports. The electroosmotic
pump can further comprise a recombination chamber coupled to the
inlet chamber to recombine an inlet chamber gas and an outlet
chamber gas. The inlet port to the inlet chamber can be configured
and positioned such that fluid entering the inlet chamber becomes
well mixed. The fluid can be well mixed by providing the fluid from
the inlet port into the inlet chamber at a high average velocity.
The high average velocity of the fluid entering the inlet chamber
at the inlet port can be greater than about 25 centimeters per
second.
[0008] In yet another aspect of the present invention, an
electroosmotic pump comprises a fluid chamber, a pumping element
for pumping fluid therethrough, the pumping element positioned to
segment the fluid chamber into an inlet chamber including a fluid
inlet port and an outlet chamber including a fluid outlet port, a
gas permeable element to allow passage of a gas from the outlet
chamber to the inlet chamber while preventing the passage of the
fluid therethrough, an inlet electrode positioned within the inlet
chamber and a predetermined distance from a first surface of the
pumping element, an outlet electrode positioned within the outlet
chamber, and means for providing electrical voltage to the inlet
electrode and the outlet electrode to produce an electrical field
therebetween, wherein the means for providing is coupled to the
inlet electrode and the outlet electrode. The gas permeable element
can allow the passage of an outlet chamber gas from the outlet
chamber to the inlet chamber. The outlet chamber gas can be
predominately hydrogen. The outlet chamber gas can be predominately
oxygen. The predetermined distance that the inlet electrode is
positioned from the first surface can be in a range of about 0.05
mm to about 5.0 mm. The outlet electrode can be positioned a
predetermined distance from a second surface of the pumping
element. The predetermined distance that the outlet electrode is
positioned from the second surface can be in a range of about 0.05
mm to about 5.0 mm. The outlet electrode can be positioned on a
second surface of the pumping element. A residence time of the
inlet chamber is in a range of about {fraction (1/20)} of a minute
to about 1 minute. A volume of the inlet chamber can be equal to an
area of the pumping element multiplied by a width of between about
0.4 cm and about 3.0 cm. The electroosmotic pump can be
manufactured using one or more materials comprising metal, glass,
ceramic, plastic, or a combination thereof. The one or more
materials can be coupled by one or more sealing materials. The one
or more sealing materials can comprise solder, sealing glass, low
modulus adhesives, or a combination thereof. Low modulus adhesives
can seal the pumping element to a housing of the electroosmotic
pump. The electroosmotic pump can be manufactured using one or more
pump materials such that each pump material is compatible with the
fluid, or such that the one or more pump materials that are not
compatible with the fluid are overcoated with a compatible
material. The fluid can comprise a buffered water solution. The one
or more pump materials can comprise insulating materials that are
compatible with buffered water solutions. The pump material can be
selected from a group consisting of silicon nitride, titania,
alumina, silica, borosilicate, vycor, and plastic. The pumping
element can exhibit a negative zeta potential in the presence of
the fluid and the inlet electrode is an anode electrode and the
outlet electrode is a cathode electrode. The pumping element can
exhibit a positive zeta potential in the presence of the fluid and
the inlet electrode is a cathode electrode and the outlet electrode
is an anode electrode. A material of the anode electrode can be
selected from the group consisting of platinum, platinum clad
niobium, platinum plated titanium, platinum clad tantalum,
graphite, glassy carbon, mixed metal oxide coating on titanium,
silver-impregnated ink, and dimensionally-stable anode material.
The mixed metal oxide coating on titanium can include an iridium
and tantalum oxide coating on titanium. The dimensionally-stable
anode material can include one from the group consisting of
conducting iridium oxide coating on titanium and ruthenium oxide
coating on titanium. A material of the cathode electrode can be
selected from a group consisting of platinum, copper, platinum
plated titanium, stainless steel, graphite, gold, plated silver,
silver-impregnated ink, and glassy carbon. The electroosmotic pump
can include one or more inlet chambers, one or more pumping
elements, and one or more outlet chambers, wherein each inlet
chamber includes one or more fluid inlet ports. The electroosmotic
pump can also include a recombination chamber coupled to the inlet
chamber to recombine an inlet chamber gas and an outlet chamber
gas. The inlet port to the inlet chamber can be configured and
positioned such that fluid entering the inlet chamber becomes well
mixed. The fluid can be well mixed by providing the fluid from the
inlet port into the inlet chamber at a high average velocity. The
high average velocity of the fluid entering the inlet chamber at
the inlet port can be greater than about 25 centimeters per
second.
[0009] Other features and advantages of the present invention will
become apparent after reviewing the detailed description of the
preferred embodiments set forth below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 illustrates a schematic diagram of a closed loop
cooling system in accordance with the present invention.
[0011] FIG. 2A illustrates an exploded view of the pump assembly in
accordance with the preferred embodiment of the present
invention.
[0012] FIG. 2B illustrates an exploded view of a pump assembly in
accordance with an alternative embodiment of the present
invention.
[0013] FIG. 3A illustrates a front side view of the bottom housing
portion in accordance with the preferred embodiment of the present
invention.
[0014] FIG. 3B illustrates a front side view of the bottom housing
portion in accordance with the alternative embodiment of the
present invention.
[0015] FIG. 4A illustrates a back side exploded view of the bottom
housing portion in accordance with preferred embodiment of the
present invention.
[0016] FIG. 4B illustrates a back side exploded view of the bottom
housing portion in accordance with the alternative embodiment of
the present invention.
[0017] FIG. 5A illustrates a cross sectional view of the pump
assembly in accordance with the preferred embodiment of the present
invention.
[0018] FIG. 5B illustrates a cross sectional view of an alternative
pump assembly in accordance with the alternative embodiment of the
present invention.
[0019] FIG. 6A illustrates a cross sectional view of the electrical
contacts used in the preferred pump assembly in accordance with the
present invention.
[0020] FIG. 6B illustrates a cross sectional view of the electrical
contacts used in the alternative pump assembly in accordance with
the present invention.
[0021] FIG. 7A illustrates a cut-away view of the preferred pumping
element with electrical contact positioned a predetermined distance
therefrom in accordance with the present invention.
[0022] FIG. 7B illustrates a cut-away view of the preferred pumping
element with electrical contact coupled thereto in accordance with
the present invention.
[0023] FIG. 8 illustrates a cross sectional view of another
alternative pump assembly in accordance with the present
invention.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0024] FIG. 1 illustrates a schematic diagram of a closed loop
cooling system 10 in accordance with the present invention. The
cooling system preferably includes a microchannel heat exchanger 12
coupled to a heat source 99, such as a microprocessor.
Alternatively, the heat exchanger 12 is integrally formed with the
heat source 99 as one component. It should be noted that the system
10 incorporates any type of heat exchanger.
[0025] As shown in FIG. 1, the outlet fluid port 16 of the heat
exchanger 12 is coupled to the fluid line 18 which is coupled to
the inlet fluid port 24 of the heat rejecter 20. The outlet fluid
port 26 of the heat rejecter 20 is coupled to the fluid line 18
which is coupled to the fluid inlet port 28 of the pump 22 of the
present invention. The outlet fluid port 30 of the pump 22 is
coupled to the fluid line 18 which is coupled to the fluid inlet
port 14 of the heat exchanger 12. The pump 22 of the present
invention pumps and circulates fluid within the closed loop 10. In
one embodiment, the present circulation system 10 includes more
than one heat exchanger 12. In another embodiment, the present
circulation system 10 includes more than one heat rejecter 20. It
is also contemplated that more than one heat source 99 can be
cooled within the circulation system 10. Alternatively, multiple
pumps (not shown) circulate fluid to their respective inlet and
outlet ports 14, 16, 24, 26 in the event there are more than one
heat exchanger 12 and more than one heat rejecter 20. It is
apparent to one skilled in the art that other components not shown
in FIG. 1 are contemplated. It is also apparent to one skilled in
the art that the components of the system 10 can be placed in any
other appropriate order in the loop 10 and the order is not limited
to the configuration shown in FIG. 1.
[0026] Preferred operation of the circulation system 10 involves
cooling the heat source 99, whereby the pump 22 circulates cooled
fluid through its outlet port 30 to the heat exchanger 12. The pump
22 of the present invention preferably circulates a uniform flow to
the heat exchanger 12 and heat rejecter 20 and is configured to
pump fluid undergoing either one or two phase flow within the
system 10 depending upon circumstances. Alternatively, the pump 22
can vary the flow to the heat exchanger 12. The fluid exiting from
the pump 22 enters the heat exchanger 12 and absorbs the heat
generated by the heat source 99. Within the heat exchanger 12, the
fluid experiences either single or two phase flow depending on a
variety of factors, including but not limited to the amount of heat
generated by the heat source 99, the amount and flow rate of the
fluid through the heat source as well as other factors. The heated
fluid exits the heat exchanger 12 through the outlet port 16 and
enters the inlet port 24 of the heat rejecter 20, whereby the heat
rejecter 20 releases the heat within the fluid into the surrounding
air and cools the fluid. The cooled fluid exits the heat rejecter
20 via the outlet port 26 and enters the pump 22 via the inlet port
28. This process continues to keep the overall system 10 or heat
source 99 operating at a desired maximum temperature.
Alternatively, this process continues to keep each of more than one
individual components in the system 10 operating at desired
temperatures.
[0027] The fluid in the cooling system 10 is preferably
water-based. Alternatively, the fluid in the system 10 is a
combination of organic solutions which provide a low freezing
temperature or enhanced thermal characteristics, as well as
resistance to corrosion. The fluid within the system can exhibit a
single-phase liquid state or two phase flow. The two phase flow
includes a fluid which is both liquid as well as vapor states.
However, whether a single-phase or a two-phase system, it is
apparent to one skilled in the art that at equilibrium and at all
operating or storage temperatures, the fluid will exhibit some
vapor in the loop 10 as well as the components such as tubes, heat
exchangers, pumps, manifolds, fittings and connectors.
[0028] FIG. 2A illustrates an exploded view of a pump assembly in
accordance with the preferred embodiment of the present invention.
As shown in FIG. 2A, a preferred pump 100 includes a housing body
having a bottom housing portion 102A and a housing lid 102B. In
addition, the pump 100 includes a fluid inlet port 126 and a fluid
outlet port 124 as well as an outlet electrode 112B' and an inlet
electrode 112A'. The outlet electrode 112B' is coupled to an outlet
electrical contact 112B, and the inlet electrode 112A' is coupled
to an inlet electrical contact 112A. The outlet electrical contact
112B and the inlet electrical contact 112A each preferably coupled
to the pump 100 through the bottom housing portion 102A. The bottom
housing portion 102A preferably includes a cavity 106 which holds
an electroosmotic pumping element 104 within. According to the
preferred embodiment, the pumping element 104 is a glass frit. The
bottom portion 102A also includes a recombination cavity 108 which
serves to recombine hydrogen and oxygen formed within the cooling
system into water. The theory of how hydrogen and oxygen is formed
within the pump due to electroosmosis is well known in the art and
will not be discussed in more detail herein. If a liquid other than
the water is pumped, it will be understood that other gases or
chemicals can be formed.
[0029] The outlet electrode 112B' and the inlet electrode 112A' are
each preferably spaced a predetermined distance from the pumping
element 104. In this preferred case, the outlet electrode 112B' and
the inlet electrode 112A' are referred to as off-frit electrodes.
Preferably, the inlet electrode 112A' is mechanically coupled to
but electrically insulated from the housing 102A, and the outlet
electrode 112B' is mechanically coupled to but electrically
insulated from the bottom surface of the cavity 106 within the
housing portion 102A. Both electrodes are preferably coupled to the
housing 102A. The inlet electrode 112A' is either coupled to the
housing 102A directly or coupled via an intermediate support
structure. Irrespective of the manner in which the inlet electrode
112A' is coupled to the housing 102A, the inlet electrode 112A' is
positioned a predetermined distance from the corresponding nearest
surface of the pumping element 104 (top surface of the pumping
element 104 in FIG. 2A). The predetermined distance between the
inlet electrode 112A' and the pumping element 104 is preferably
within a range of about 0.05 mm to about 5.0 mm. Similarly, the
outlet electrode 112B' is either coupled to the housing portion
102A directly or coupled via an intermediate support structure. The
outlet electrode 112B' is preferably positioned a predetermined
distance from the corresponding nearest surface of the pumping
element 104 (bottom surface of the pumping element 104 in FIG. 2A).
The predetermined distance between the outlet electrode 1112B' and
the pumping element 104 is preferably within a range of about 0.05
mm to about 5.0 mm.
[0030] The inlet electrode 112A' and the outlet electrode 112B' can
be a wire mesh, a perforated foil, a loose spiral, clad metal
foils, expanded metal foils, or a film deposited on the inner
surface of the housing portion. Other types of electrodes can also
be used as the inlet electrode 112A' and the outlet electrode
112B'. Examples of such alternative electrodes are described in the
co-filed, co-pending and co-owned U.S. Patent Application Ser. No.
______ (Cool 00700), filed on ______, entitled "Micro-fabricated
Electrokinetic Pump with On-Frit Electrode", which is hereby
incorporated by reference. The material used for an anode electrode
is preferably selected from the group consisting of platinum,
platinum clad niobium, platinum plated titanium, platinum clad
tantalum, graphite, glassy carbon, mixed metal oxide coating on
titanium such as iridium and tantalum oxide coating on titanium,
silver-impregnated ink, and dimensionally-stable anode material
such as conducting iridium oxide or ruthenium oxide coating on
titanium. The material used for a cathode electrode is preferably
selected from the group consisting of platinum, copper, platinum
plated titanium, stainless steel, graphite, gold, plated silver,
silver-impregnated ink, and glassy carbon.
[0031] FIG. 2B illustrates an exploded view of a pump assembly in
accordance with an alternative embodiment of the present invention.
As shown in FIG. 2B, an alternative pump 200 includes a housing
body having a bottom housing portion 202A and a housing lid 202B.
The pump 200 is identical to the pump 100 with the exception that
an outlet electrode 212B' and an inlet electrode 212A'are coupled
to the pumping element 204. In this alternative case, the outlet
electrode 212B' and the inlet electrode 212A' are referred to as
on-frit electrodes.
[0032] FIG. 3A illustrates a perspective frontal view of the
receiving area of the bottom housing portion 102A in accordance
with the preferred embodiment of the present invention. In
addition, FIG. 4A illustrates a perspective rear exploded view of
the outer surface of the bottom housing portion 102A in accordance
with the preferred embodiment of the present invention. As shown in
FIGS. 3A and 4A, the preferred bottom housing portion 102A includes
a bottom surface 118A, side walls 114A, 114B, 116A, 116B. A top lip
118B is formed peripheral with the sidewalls 114A, 114B, 116A, and
116B around the entire bottom housing portion 102A. The top lip
118B is shaped to align with and attach to the outer lip 103 (FIG.
2A) of the housing lid 102B. As shown in FIG. 5A, the lip 103 of
the housing lid 102B and the top lip 118B of the bottom housing
102A create a seal when bonded or mated in contact with one
another, thereby forming a sealed environment within the pump 100.
Although the side walls 114A, 114B, 116A, and 116B preferably form
a rectangular housing portion 102A, it is apparent to one skilled
in the art that the rectangular housing portion can have any other
appropriate shape (e.g. circular, square, trapezoidal, any other
polygon, or combinations of parts of a circle and a polygon).
[0033] Referring back to FIG. 3A, the bottom housing portion 102A
has the receiving cavity 106 and the recombination cavity 108,
whereby a barrier wall 122 is positioned therebetween to separate a
portion of the receiving cavity 106 from the recombination cavity
108. Preferably, the receiving cavity 106 is circular in shape,
such that a circular electroosmotic pumping element 104 fits
securely within. Preferably, the shape of the outlet electrode
112B' and the inlet electrode 112A' (not shown in FIG. 3A)
substantially matches the shape of the pumping element 104.
Alternatively, the shape of the inlet electrode 112A' and the
outlet electrode 112B' do not match the shape of the pumping
element 104. Although the electroosmotic pumping element 104 (FIGS.
2A and 3A) has a circular disk-shape, other pumping element shapes
are contemplated. Thus, the cavity 106 alternatively has a shape
corresponding with the shape of the pumping element 104.
[0034] FIG. 3B illustrates a perspective frontal view of the
receiving area of the bottom housing portion 202A in accordance
with the alternative embodiment of the present invention
illustrated in FIG. 2B. In this alternative embodiment, the outlet
electrode 212B' and the inlet electrode 212A' are coupled to the
pumping element 204, in other words the outlet electrode 212B' and
the inlet electrode 212A' are on-frit electrodes. As such, the
outlet electrode 212B' is not coupled to the bottom housing portion
202A. Since FIG. 3B illustrates the bottom housing portion 202A,
the inlet electrode 212A' is not shown in FIG. 3B.
[0035] As shown in FIGS. 2A and 3A, the cavity 106 preferably
includes a beveled edge 120 in the interior bottom surface. The
pumping element 104 and housing 102 are preferably made of
borosilicate glass, whereby both have a matching coefficient of
thermal expansion (CTE) value. Therefore, the pumping element 104
as well as the housing 102 thermally expand at the same rate during
operation. The bottom surface of the pumping element 104 sits on
the edge 120 to create an outlet chamber 140 (FIG. 5A) below the
pumping element 104 and an inlet chamber 142 (FIG. 5A) above the
pumping element 104. The pumping element 104 is coupled to the edge
120 preferably by sealing glass, whereby fluid in the inlet chamber
142 is pumped through the pumping element 104. Alternatively, the
pumping element 104 is coupled to the edge 120 by an adhesive or
preferably a low modulus adhesive.
[0036] As shown in FIGS. 3A and 4A, the bottom housing portion 102A
includes an inlet port 126 and an outlet port 124 preferably
extending away from the outer bottom surface 118A of the bottom
housing portion 102A. It is preferred that the fluid inlet port 126
and the fluid outlet port 124 extend from the same surface in the
housing to allow the pump 100 to be placed in a small space.
Alternatively, the inlet and outlet ports 126, 124 are configured
to extend from different surfaces of the pump 100 housing.
Referring to FIGS. 3A and 4A, the inlet port 126 leads into the
cavity 106 and is in communication with the inlet fluid chamber
142. In addition, the inlet port 126 extends from the bottom
surface 118A through the bottom housing portion 102A to the opening
near the lip 118B of the bottom housing portion 102A. Fluid
traveling through the inlet port 126 is kept separate from the
fluid which travels through the outlet port 124. In addition, it is
apparent to one skilled in the art that although only one inlet and
one outlet port are shown and described herein, any number of inlet
and outlet ports and fluid lines are alternatively used with the
pump 100 of the present invention.
[0037] The orientation of the pump is an important factor to
consider when choosing the location of the outlet port 124. In the
preferred embodiment, the pumping element has a negative zeta
potential. As such, the outlet electrode 112B' in the outlet
chamber 140 (FIG. 5A) generates H.sub.2 gas during the operation of
the electrokinetic pump. The H.sub.2 gas eventually reaches the
inlet chamber 142 (FIG. 5A) of the pump in order to recombine with
the O.sub.2 at the catalyst to regenerate H.sub.2O. A preferred
arrangement of the pump 100, as shown in FIG. 5A, includes the
inlet port 126 positioned at or near the top of the inlet chamber
142. This configuration allows bouyancy to assist in the movement
of the H.sub.2 bubbles from the outlet electrode 112B' to the
outlet port 124, whereby the H.sub.2 bubbles are pushed through the
fluid loop back to the inlet chamber 142 of the pump 100 and are
recombined at the recombination chamber 108. Due to this effect,
the pump 100 is oriented such that the recombination chamber 108 is
positioned above the pump element 104.
[0038] FIG. 5A illustrates a cross sectional view of the preferred
pump assembly 100 in accordance with the present invention. The
pumping element 104 sits on the edge 120 to form the outlet chamber
140 below the pumping element 104 and the inlet chamber 142 above
the pumping element 104. The chamber that includes the inlet
electrode is referred to as the inlet chamber, which in FIG. 5A
also corresponds to the inlet chamber 142. The chamber that
includes the outlet electrode is referred to as the outlet chamber,
which in FIG. 5A also corresponds to the outlet chamber 140. The
size of the inlet chamber is preferably configured according to a
predetermined residence time. The residence time is defined as the
volume of the inlet chamber divided by the flow rate. For example,
if the inlet chamber has a volume of 1 liter and the flow rate is 1
liter/minute, than the average residence time is 1 minute. In the
preferred embodiment, the residence time is in a range of about
{fraction (1/20)} of a minute to about 1 minute. The configured
volume of the inlet chamber scales with the anticipated flow rate
of the pump assembly to achieved the desired residence time.
[0039] The volume of the inlet and outlet chambers is preferably
designed so as to allow for the required residence times of between
{fraction (1/20)} of a minute and 1 minute. In order to achieve
these residence times, the inlet chamber is preferably sized so as
to have volume equal to the area of the porous pumping element
multiplied by a width of between about 0.4 cm and about 3 cm. The
outlet chamber can also be similarly sized. The fluid inlets and
outlets from these chambers are preferably designed so as to induce
some mixing of the fluids within these chambers. The fluid in the
inlet chamber is considered well mixed when the standard deviation
of the average pH of the fluid in the inlet chamber is preferably
less than 3 pH points. More preferably the standard deviation of
the pH is less than 2 pH points. Most preferably the standard
deviation of the pH is less than 1 pH point. In order for the fluid
in the inlet chamber to become well mixed, the average fluid
velocity of the fluid entering the inlet chamber at the inlet port
is of high average velocity. High average velocity is preferably
greater than 10 cm/sec. More preferably, high average velocity is
greater than 20 cm/sec. Most preferably, high average velocity is
greater than 25 cm/sec.
[0040] Referring to FIGS. 3A and 4A, the bottom housing portion
102A preferably includes two ports 128, 130 which are configured to
hold the inlet and outlet electrical contacts 112A, 112B,
respectively. In particular, the contact port 130 extends from the
cavity 106 and preferably protrudes out from the bottom surface
118A. In addition, the contact port 128 protrudes out from the
bottom surface 118A and preferably extends through the body of the
bottom housing portion 102A to the lip 118B of the bottom housing
portion 102A. As shown with respect to FIGS. 3A and 4, the outlet
electrical contact 112B fits within the electrical port 130,
whereby the outlet electrical contact 112B is in contact with the
outlet electrode 112B'. In addition, the inlet electrical contact
112A fits within the electrical port 128, whereby the inlet
electrical contact 112A is in contact with the inlet electrode
112A'.
[0041] The housing 102 of the present pump 100 is made of a
material such that electrical contact provided to the pumping
element 104 does not short-out the pump 100. Preferably, the
housing 102 is made of an insulating material, including but not
limited to glass, ceramic, plastic, polymer or a combination
thereof. Alternatively, the housing 102 is made of any appropriate
metal which has its inside surface coated with any of the above
specified insulating materials.
[0042] It is also preferable that the materials selected for the
pump, and the other components in the system 10 (FIG. 1), are
compatible with the fluid used in the system 10. As described
above, the fluid used in the system 10 is preferably water-based.
More preferably, the fluid is a buffered water solution with a high
pH. With such a fluid, there are materials that are likely to
corrode or decompose, such as Aluminum. However, there are many
metals, ceramics and glasses that are compatible with a high pH
buffered water solution. Preferred metals include, but are not
limited to, copper, titanium, stainless steel, platinum, silver,
gold, niobium, and nickel. Preferred ceramics include, but are not
limited to, silicon nitride, titania, alumina, and silica.
Preferred glasses include, but are not limited to, silica,
borosilicate, and vycor.
[0043] Certain pumping element materials, such as silica, in
combination with fluids of certain pH range are known to have a
negative zeta potential. When this combination of fluid and pump
material are used, fluid flow moves from anode to cathode.
Alternatively, other pumping element materials, such as alumina,
when combined with fluid of a certain pH range, exhibit positive
zeta potential. When this combination of fluid and pump material
are used, fluid flow moves from cathode to the anode.
[0044] As know in the art, a result of operating an electroosmosis
pump is that O.sub.2 is generated at the inlet electrode. Some of
the generated O.sub.2 takes the form of dissolved O.sub.2 in the
fluid. An undesired consequence is that the dissolved O.sub.2 can
react with organic materials, such as epoxy, at any location in the
cooling loop of system 10 (FIG. 1). If the dissolved O.sub.2 does
react with the organic material, the O.sub.2 is removed from the
system which leaves an excess H.sub.2, gradually contributing to
pressure increases inside the system. This effect can be limited by
reducing or limiting the fraction of the inside surface of the
entire system that is organic. In one embodiment of the present
invention, the pump assembly 100, 200 is comprised solely from
non-reacting materials, such a glass, sealing glass, metals, and
ceramics. In this case, solder and/or sealing glass are used as
joining materials, instead of using epoxy. In another embodiment,
where the use of epoxy is desired, the areas inside the pump
assembly in which the epoxy is exposed to the fluid are limited by
proper design. The exposed areas can also be coated with a
non-reactive coating and/or the exposed surface can be pre-treated
so that it is already oxidized and therefore inert to further
oxidation.
[0045] It is also contemplated that other fluids can be used within
the system 10, and the materials used for the components of the
system 10 are any materials compatible with the selected fluid,
e.g. any material with negligible or no corrosion or decomposition
in the presence of the selected fluid.
[0046] Referring back to FIG. 5A, an inlet fluid tube 138 is
coupled to the inlet fluid port 126. Preferably, a sealing collar
144 is positioned between the inner surface of the fluid tube 136
and the fluid port 126. The sealing collar 144 is preferably made
of Tungsten or other appropriate material which has a CTE that
approximately matches the material of the fluid port 126. Since the
CTE of the sealing collar 144 material approximates that of the
fluid port 126 material, the CTE of the sealing collar 144 material
will probably not match that of the fluid tube material 138.
However, the sealing collar 144 preferably includes an appropriate
ductility to maintain a seal with the fluid tube 138 material
regardless of the amount of expansion or contraction experienced by
the fluid tube 138. The sealing collar 144 is preferably also
positioned between the outlet fluid port 124 and an outlet fluid
line 136. Although the sealing collar 144 is described in relation
to the pump 100, it is apparent to one skilled in the art that the
sealing collar 144 can also be used to couple the fluid lines and
the inlet and outlet ports of the other components in the system 10
(FIG. 1), including but not limited to the heat exchanger 12 and
the heat rejecter 20.
[0047] The sealing collar 144 is applied between the fluid tube
136, 138 and the fluid ports 124, 126 by preferably heating the
fluid tube 136, 138 to a temperature whereby the fluid tube 136,
138 expands to allow a slip fit over the sealing collar 144. The
sealing collar 144 is then inserted within the tube 136, 138 and
the tube 136, 138 is allowed to cool and contract, forming a seal
around the sealing collar 144. Prior to completing this assembly,
the sealing collar 144 is coupled to the fluid port 124, 126 by any
appropriate method including, but not limited to, sealing glass,
solder, melting the glass, and joining with epoxy. Alternatively,
the sealing collar 144 is coupled to the fluid port 124, 126 during
the glass molding or pressing process of forming the housing 102.
The pumping element 104 and the housing components are preferably
attached using these same processes. The order of the steps of
assembling the pump 100 is determined by the temperatures of the
components in each step as well as the desire to protect certain
elements of the pump 100 from certain temperatures. For example, if
the catalyst has an upper thermal exposure limit of 400 C, it is
desired to carry out higher temperature assembly steps prior to the
sealing of the recombination chamber 108 with the catalyst element
inside.
[0048] The fluid tubes 136, 138 are preferably coupled to the fluid
ports 124, 126 via the sealing collar 144, as described above.
Alternatively, the fluid tubes 136, 138 are hermetically coupled to
the fluid ports 124, 126 using alternative means including, but not
limited to, placing a sealing material between the sealing collar
and the fluid port and/or placing a sealing material between the
sealing collar and the fluid tube, inserting the fluid tube
directly into the fluid port without use of the sealing collar, and
inserting the fluid tube into the fluid port with a sealing
material placed there between without use of the sealing collar.
Examples of such sealing means are described in greater detail in
the co-filed, co-pending U.S. Patent Application Ser. No. ______
(Cool 2100), filed on ______, entitled "Hermetic Closed Loop Fluid
System", which is hereby incorporated by reference.
[0049] A preferred process for assembling the pump 100 involves
using sealing glass or low modulus adhesive to couple the porous
pumping element 104 to the cavity 106 within the housing 102 as
well as to couple the seals between the housing ports 124, 126 and
the sealing collars 144. Electrical feedthroughs are preferably
formed in the next step. Following, the housing components 102A,
102B are combined with the electrodes 112A', 112B' and catalyst
within. Following, the housing 102 is sealed using a
low-temperature solder reflow or an epoxy seal. The fluid tubes
136, 138 are then preferably heated and sealed around the sealing
collars 144.
[0050] FIG. 5B illustrates a cross sectional view of the
alternative pump assembly 200 in accordance with the present
invention. In the alternative pump assembly 200, the inlet
electrode 212A' (not shown) is coupled to the top surface of the
pumping element 204, and the outlet electrode 212B' (not shown) is
coupled to the bottom surface of the pumping element 204. As shown
with respect to FIGS. 2B, 4B and 5B, the outlet electrical contact
212B fits within the electrical port 230 to make contact with the
outlet electrode 212B', whereby the outlet electrode 212B' is in
contact with the outlet side of the pumping element 204. In
addition, the inlet electrical contact 212A fits within the
electrical port 228 to make contact with the inlet electrode 212A',
whereby the inlet electrode 212A' in contact with the inlet side of
the pumping element 104.
[0051] FIG. 6A illustrates a cross sectional view of the electrical
contacts 112A, 112B used in the preferred electroosmotic pump
assembly 100 of the present invention. As shown in FIG. 6A, the
inlet electrical contact 112A is positioned within the inlet port
128 and the outlet electrical contact 112B is positioned within the
outlet port 130. Preferably the electrical contacts 112A, 112B are
positioned in the housing portion 102A through the same outer
surface, such as the bottom surface 118A (FIG. 4A), to allow the
pump 100 to fit in smaller areas within the electronic device.
Alternatively, the electrical contacts 112A, 112B are positioned in
the pump 100 through different outer surfaces of the housings 102A,
102B.
[0052] Similar to the fluid tubes 136, 138, the electrical contacts
112A, 112B are preferably made of copper which has a CTE that
typically mismatches the CTE of the housing 102 material. Thus,
expansion of the copper electrical contacts 112A, 12B at a rate
faster than the housing 102 material will cause the electrical
contacts 112A, 112B to press against the inner walls of their
respective ports and improve the pressure of the seal between the
housing 102 and the electrical contacts 112A, 112B. In an extreme
case, the increased pressure exceeds the material strength of the
housing material and leads to cracks forming in the housing 102. In
contrast, expansion of the housing 102 material at a rate faster
than that of the electrical contacts 112A, 112B will cause a gap in
the seal between each electrical contact 112A, 112B and its
respective electrical contact port 128, 130, thereby also
jeopardizing the sealed environment within the pump 100 and system
10 (FIG. 1). To allow the electrical contacts 112A, 112B and
housing 102 to thermally expand at different rates while
maintaining the sealed environment of the pump 100 and system 10,
the sealing collar 144 is preferably positioned between the inner
surface of the contact ports 128, 130 and the electrical contact
112A, 112B. The sealing collar 144 is preferably made of tungsten
or other appropriate material which has a CTE that approximately
matches the housing 102 material. The sealing collar 144 also has
an appropriate ductility to provide a tolerance buffer between the
electrical contact 112A, 112B and the electrical contact ports 128,
130 such that the electrical contacts 112A, 112B and ports 128, 130
are allowed to expand and contract at their respective rates
without forfeiting the sealed environment within the housing
102.
[0053] The sealing collar 144 is preferably secured to the
electrical contacts 112A, 112B and the contact ports 128, 130 by
using a sealing glass therebetween. Alternatively, the sealing
collar 144 is secured to the electrical contact 112 and the ports
128, 130 using solder. Alternatively, instead of using a sealing
collar 144 between the contacts 112A, 112B and the ports 128, 130
housing, the electrical contacts 112A, 112B themselves may be made
of tungsten or any other appropriate material, such that the
electrical contact 112A, 112B expands along with the housing 102
and maintains the environment within the pump 100. Alternatively,
sealing methods similar to those described above in relation to
coupling the fluid tubes 136, 138 to the fluid ports 124, 126 can
be used to seal the electrical contacts 112A, 112B to the housing
102.
[0054] FIG. 6B illustrates a cross sectional view of the electrical
contacts used in the alternative pump assembly 200 in accordance
with the present invention. As shown in FIG. 6B, the inlet
electrical contact 212A is positioned within the inlet port 228 and
is coupled to the on-frit inlet electrode 212A', and the outlet
electrical contact 212B is positioned within the outlet port 230
and is coupled to the on-frit outlet electrode 212B'.
[0055] It is understood that the aforementioned description related
to the preferred pump assembly 100 of FIGS. 2A, 3A, 4A, 5A, and 6A
apply similarly to the alternative pump assembly 200 of FIGS. 2B,
3B, 4B, 5B, and 6B with the exception of the on-frit electrodes of
pump 200 versus the off-frit electrodes of pump 100.
[0056] FIG. 7A illustrates a cut-away view of the preferred pump
assembly 100 with the inlet electrical contact 112A coupled to an
off-frit electrode 146 preferably disposed on the inner surface of
the housing lid 102B, where the off-frit electrode 146 is
preferably positioned a predetermined distance from the pumping
assembly 104. As shown in FIG. 7A, the inlet electrical contact
112A is coupled to the off-frit electrode 146 by a solder or
conductive epoxy 148. Preferably, an epoxy 150 is disposed over the
electrical contact 112A and attaching material 148 to passivate and
thereby protect the attaching material 148. Similarly, the outlet
electrical contact 112B (not shown) is coupled to a second off-frit
electrode (not shown) preferably disposed on the inner surface of
the bottom housing portion 102A, where the second off-frit
electrode is preferably positioned a predetermined distance from
the pumping assembly 104. The outlet electrical contact 112B is
coupled to the second off-frit electrode by a solder or conductive
epoxy, and an epoxy is preferably disposed over the electrical
contact 112B and attaching material.
[0057] FIG. 7B illustrates a cut-away view of the alternative pump
assembly 200 with the inlet electrical contact 212A coupled thereto
in accordance with the present invention. As shown in FIG. 7B, the
inlet electrical contact 212A is coupled to an on-frit electrode
246 disposed on the surface of the pumping element 204 by a solder
or conductive epoxy 248. More details regarding the on-frit
electrode 246 are shown and described in co-pending U.S. Patent
Application Ser. No. ______ (Cool-00700), filed Sep. 23, 2003,
entitled "Micro-fabricated Electrokinetic Pump with On-frit
Electrode", which is hereby incorporated by reference. In the case
of a solder being used as the attaching material 248, electrical
current applied to the electrical contact 212A causes the solder
joint to corrode. Alternatively, in the case of a conductive epoxy
being used as the attaching material 248, electrical current
applied to the electrical contact 212A causes silver corrosion to
occur. To prevent the corrosion from occurring, an epoxy 250 is
disposed on top of the electrical contact 212A and attaching
material 248 to passivate and thereby protect the attaching
material 248. The same applies to the outlet electrical contact
212B (not shown) as to the inlet electrical contact 212A.
[0058] As described in detail above, when an epoxy is used as part
of the pump assembly, such as conductive epoxy 148, 248 and epoxy
150, 250 (FIGS. 7A and 7B), it is preferred that the epoxy is
coated with a non-reactive coating or the epoxy is pre-treated such
that an epoxy area exposed to the fluid within the system is inert
to further oxidation.
[0059] Operation of the electroosmotic pump 100 will now be
discussed in detail with reference to FIG. 5A. As shown by the
arrows in FIG. 5A, fluid enters the pump 100 preferably through the
fluid inlet port 126, whereby the fluid flows into the fluid inlet
chamber 142. The pumping element 104 positioned below the fluid
inlet chamber 142 draws substantially all of the fluid from the
fluid inlet chamber 142 through the individual fluid pathways in
the pumping element 104 by electroosmosis. The fluid is pumped
through the pumping element 104, whereby the fluid flows to the
outlet fluid chamber 140 below the pumping element 104. The fluid
pumped into the fluid outlet chamber 140 flows to the outlet port
124. As stated above, the inlet port 126 extends through the body
of the bottom housing portion 102A and does not allow fluid flowing
through the inlet port to mix or come into contact with the fluid
entering the fluid outlet chamber 140. The fluid then exits out of
the outlet port 124 through the fluid line 136 to the downstream
components in the loop 10.
[0060] In operation of the preferred embodiment, in which the
pumping element has a negative zeta potential, the recombination
chamber 108 preferably stores excess oxygen generated on the low
pressure side of the pumping element 104 which does not travel with
the circulating fluid. Thus, as excess oxygen is generated within
the pump 100, the gas flows naturally to the recombination chamber
108 and remains within the chamber 108. Meanwhile, excess hydrogen
is generated on the high pressure side of the pumping element 104.
The excess hydrogen is carried along with the fluid flow and enters
the recombination chamber 108, wherein the excess hydrogen gas and
oxygen gas recombines into water which is output from the pump 100.
The alternative electroosmotic pump 200 operates in a similar
fashion as that described above in relation to pump 100.
[0061] Although the pump assembly has been described such that the
inlet and outlet electrodes are either both off-frit electrodes
(pump assembly 100) or both on-frit electrodes (pump assembly 200),
the pump assembly can also be configured such that one of the
electrodes is an on-frit electrode and the other electrode is an
off-frit electrode.
[0062] FIG. 8 illustrates a cross sectional view of an alternative
pump assembly 300. The pump assembly 300 includes a means for
allowing the gas generated in the outlet electrode chamber to be
brought directly to the inlet chamber without passing through the
entire loop of system 10 (FIG. 1). A semipermeable element 321
which allows the passage of gas without allowing the passage of
fluid is positioned near the top of the outlet chamber 340. As
such, H.sub.2 gas generated in the outlet chamber 340 is allowed to
rise to this semipermeable element 321, and travel directly to the
inlet chamber 342. The H.sub.2 gas rises with the O.sub.2 generated
in the inlet chamber 342 to the recombination chamber 308. The
semipermeable element 321 can be comprised of many materials,
including a porous structure, a hydrophobic mesh material, or any
other material or structure which preferentially allows gas to pass
without allowing fluids to pass. Several examples of such a bypass
are described in the pending U.S. Patent Application No.
2003/0164231, published on Sep. 4, 2003, and entitled
"Electroosmotic Microchannel Cooling System", which is hereby
incorporated by reference. The semipermeable element 321 is mounted
in the housing 302A using low-modulus adhesive, sealing glass, or
by any other means described herein.
[0063] Although embodiments of the electrokinetic pump described
herein are directed to a single inlet chamber and a single outlet
chamber, it is understood that the electrokinetic pump can include
one or more inlet chambers, one or more pumping elements, and one
or more outlet chambers. Each inlet chamber can include one or more
fluid inlet ports.
[0064] The figures are provided for illustrative purposes and to
aid in the understanding of the present invention. Certain
descriptive terms, such as up, down, below and above, are used
relative to the figures being described. Such descriptions are not
intended to limit the operational orientation of the present
invention.
[0065] The present invention has been described in terms of
specific embodiments incorporating details to facilitate the
understanding of the principles of construction and operation of
the invention. Such reference herein to specific embodiments and
details thereof is not intended to limit the scope of the claims
appended hereto. It will be apparent to those skilled in the art
that modifications may be made in the embodiment chosen for
illustration without departing from the spirit and scope of the
invention.
* * * * *