U.S. patent application number 10/850673 was filed with the patent office on 2009-05-07 for micro fuel cell.
Invention is credited to Tom Rezachek, Roland A. Wood.
Application Number | 20090117413 10/850673 |
Document ID | / |
Family ID | 34753197 |
Filed Date | 2009-05-07 |
United States Patent
Application |
20090117413 |
Kind Code |
A9 |
Wood; Roland A. ; et
al. |
May 7, 2009 |
Micro fuel cell
Abstract
A fuel cell, fuel cell array and methods of forming the same are
disclosed. The fuel cell can be made by forming a first aperture
defined by a first aperture surface through a first electrode layer
and forming a second aperture defined by a second aperture surface
through a second electrode layer. A proton exchange membrane is
laminated between the first electrode layer and the second
electrode layer. At least a portion of the first aperture is at
least partially aligned with the second aperture.
Inventors: |
Wood; Roland A.;
(Bloomington, MN) ; Rezachek; Tom; (Cottage Grove,
MN) |
Correspondence
Address: |
HONEYWELL INTERNATIONAL INC.
101 COLUMBIA ROAD
P O BOX 2245
MORRISTOWN
NJ
07962-2245
US
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20050260461 A1 |
November 24, 2005 |
|
|
Family ID: |
34753197 |
Appl. No.: |
10/850673 |
Filed: |
May 21, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10750581 |
Dec 29, 2003 |
|
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10850673 |
May 21, 2004 |
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Current U.S.
Class: |
429/416 ;
156/252; 156/256 |
Current CPC
Class: |
H01M 2250/30 20130101;
Y02E 60/523 20130101; Y02B 90/18 20130101; H01M 8/1011 20130101;
H01M 8/04089 20130101; Y02B 90/10 20130101; H01M 8/0247 20130101;
H01M 8/1023 20130101; Y02E 60/50 20130101; Y10T 156/1056 20150115;
H01M 8/1004 20130101; Y10T 156/1062 20150115; H01M 8/1039 20130101;
H01M 8/241 20130101 |
Class at
Publication: |
429/012 ;
429/018; 156/252; 156/256 |
International
Class: |
H01M 8/00 20060101
H01M008/00 |
Claims
1. A method of forming a fuel cell, comprising the steps of:
providing a first substrate with a first aperture extending through
the first substrate; providing a second substrate with a second
aperture extending through the second substrate; laminating a
proton exchange membrane between the first substrate and the second
substrate where the first aperture is at least partially aligned
with the second aperture.
2. A method according to claim 1 wherein the proton exchange
membrane includes a catalyst.
3. A method according to claim 1, wherein an inner surface of the
first substrate facing the proton exchange membrane extends beyond
the proton exchange membrane in at least one region, and an inner
surface of the second substrate facing the proton exchange membrane
extends beyond the proton exchange membrane in the at least one
region.
4. A method according to claim 3 further comprising the step of
providing an adhesive between the inner surface of the first
substrate and the inner surface of the second substrate in the at
least one region.
5. A method according to claim 1 further comprising the steps of:
providing a first conductive layer on an inner surface of the first
substrate facing the proton exchange membrane adjacent to the first
aperture; and providing a second conductive layer on an inner
surface of the second substrate facing the proton exchange membrane
adjacent to the second aperture.
6. A method according to claim 5 wherein the inner surface of the
first substrate extends beyond the proton exchange membrane in at
least one interconnect region, and the inner surface of the second
substrate extends beyond the proton exchange membrane in the at
least one interconnect region.
7. A method according to claim 6 wherein the first conductive layer
extends into the at least one interconnect region and the second
conductive layer extends into the at least one interconnect region
and overlaps and makes an electrical connection to the first
conductive layer.
8. A method according to claim 7, wherein the first substrate and
the second substrate are substantially non-conductive.
9. A method of forming a plurality of fuel cells, comprising the
steps of: forming a first plurality of apertures through a first
sheet; forming a second plurality of apertures through a second
sheet; and laminating a proton exchange membrane between the first
sheet and the second sheet, where the first plurality of apertures
are at least partially aligned with the second plurality of
apertures.
10. A method according to claim 9 wherein the proton exchange
membrane includes a catalyst.
11. A method according to claim 10 wherein the proton exchange
membrane includes a perfluorosulfuric acid membrane with a
polytetrafluoroethylene backbone.
12. A method according to claim 11 wherein the catalyst includes
carbon/platinum.
13. A method according to claim 9, wherein an inner surface of the
first sheet facing the proton exchange membrane extends beyond the
proton exchange membrane in at least one region, and an inner
surface of the second sheet facing the proton exchange membrane
extends beyond the proton exchange membrane in the at least one
region.
14. A method according to claim 13 further comprising the step of
providing an adhesive between the inner surface of the first sheet
and the inner surface of the second sheet in the at least one
region.
15. A method according to claim 9 further comprising the steps of:
providing two or more first conductive electrodes on an inner
surface of the first sheet facing the proton exchange membrane
adjacent to at least two of the first plurality of apertures; and
providing two or more second conductive electrodes on an inner
surface of the second sheet facing the proton exchange membrane
adjacent to at least two of the second plurality of apertures.
16. A method according to claim 15 wherein the inner surface of the
first sheet extends beyond the proton exchange membrane in at least
one interconnect region, and the inner surface of the second
substrate extends beyond the proton exchange membrane in the at
least one interconnect region.
17. A method according to claim 16 wherein at least one of the
first conductive electrodes extends into the at least one
interconnect region and at least one of the second conductive
electrodes extends into the at least one interconnect region and
overlaps and makes an electrical connection to the at least one
first conductive electrodes.
18. A method according to claim 17, wherein the first sheet and the
second sheet are substantially non-conductive.
19. A fuel cell comprising: a first substrate having a first
aperture; a second substrate having a second aperture; and a proton
exchange membrane disposed between the first substrate and the
second substrate and spanning the first aperture and the second
aperture; wherein, the first aperture is at least partially aligned
with the second aperture and the proton exchange layer is
unsupported across at least a major portion of the first aperture
and the second aperture.
20. The fuel cell according to claim 19, wherein the proton
exchange membrane has a thickness of 1 mil or less.
21. The fuel cell according to claim 20, wherein at least one of
the first aperture and the second aperture has a cross-sectional
area of 1 mm.sup.2 or less.
22. The fuel cell according to claim 20, wherein the aligned
portion of the first aperture and the second aperture has a
cross-sectional area of 1 mm.sup.2 or less.
23. The fuel cell according to claim 19, wherein the first sheet
has a thickness of 2 mil or less.
24. The fuel cell according to claim 23, wherein the second sheet
has a thickness of 2 mil or less.
25. The fuel cell according to claim 19 further comprising a first
electrode on an inner surface of the first sheet facing the proton
exchange membrane.
26. The fuel cell according to claim 25 wherein the first electrode
extends adjacent to the first aperture.
27. The fuel cell according to claim 15 further comprising a second
electrode on an inner surface of the second sheet facing the proton
exchange membrane.
28. The fuel cell according to claim 27 wherein the second
electrode extends adjacent to the second aperture.
29. A fuel cell according to claim 28 wherein the inner surface of
the first sheet extends beyond the proton exchange membrane in at
least one interconnect region, and the inner surface of the second
sheet extends beyond the proton exchange membrane in the at least
one interconnect region, and wherein the first electrode extends
into the at least one interconnect region and the second electrode
extends into the at least one interconnect region and makes an
electrical connection to the first electrode.
30. A fuel cell, comprising: a top layer having a first plurality
of electrical contacts and a first plurality of apertures where at
least selected first electrical contacts extend from adjacent
corresponding apertures to a first region; a bottom layer having a
second plurality of electrical contacts and a second plurality of
apertures wherein where at least selected second electrical
contacts extend from adjacent corresponding apertures to a second
region, wherein the first region at least partially overlaps the
second region in an overlap region; and a proton exchange membrane
disposed between the top layer and bottom layer adjacent the
apertures but not in the overlap region.
31. The fuel cell according to claim 30, wherein an adhesive layer
is disposed between the top layer and the bottom layer in the
overlap region.
32. A method of forming a plurality of fuel cells, comprising the
steps of: providing a first length of material having a first
plurality apertures and a first plurality of electrical contacts;
providing a second length of material having a second plurality
apertures and a second plurality of electrical contacts; providing
a proton exchange membrane; moving the first length of material
into a joining unit; moving the second length of material into the
joining unit such that the second plurality of apertures are at
least partially in registration with the first plurality of
apertures; and moving the proton exchange membrane into the joining
unit simultaneously with and in between the first and second length
of material, at least part of the proton exchange membrane aligned
with the plurality of first and second apertures to form a
plurality of fuel cells.
33. A method according to claim 32, wherein an inner surface of the
first length of material extends beyond the proton exchange
membrane in at least one region, and an inner surface of the second
length of material extends beyond the proton exchange membrane in
the at least one region.
34. A method according to claim 33 further comprising the step of
providing an adhesive between the inner surface of the first length
of material and the inner surface of the second length of material
in the at least one region.
35. A method according to claim 32, further comprising the step of
dicing the plurality of fuel cells into arrays of fuel cells.
36. A method of forming a fuel cell, comprising the steps of:
providing a first substrate having an inside surface and an outside
surface and a first aperture extending from the inside surface to
the outside surface; providing a first electrode layer adjacent the
first aperture on the inside surface of the first substrate;
providing a second substrate having an inside surface and an
outside surface and a second aperture extending from the inside
surface to the outside surface; providing a second electrode layer
adjacent the second aperture on the inside surface of the second
substrate; and sandwiching a proton exchange membrane between the
inside surface of the first substrate and the inside surface of the
second substrate, where the first aperture is at least partially
aligned with the second aperture with the proton exchange membrane
extending therebetween.
37. A method according to claim 36 wherein the proton exchange
membrane includes a catalyst.
38. A method according to claim 36 wherein the inner surface of the
first substrate extends beyond the proton exchange membrane in at
least one region, and the inner surface of the second substrate
extends beyond the proton exchange membrane in the at least one
region.
39. A method according to claim 38 further comprising the step of
providing an adhesive between the inner surface of the first
substrate and the inner surface of the second substrate in the at
least one region.
40. A method according to claim 36 wherein the inner surface of the
first substrate extends beyond the proton exchange membrane in at
least one interconnect region, and the inner surface of the second
substrate extends beyond the proton exchange membrane in the at
least one interconnect region.
41. A method according to claim 40 wherein the first electrode
layer extends into the at least one interconnect region and the
second electrode layer extends into the at least one interconnect
region and makes an electrical connection to the first electrode
layer.
Description
[0001] This application claims priority to U.S. patent application
Ser. No. 10/750,581, filed Dec. 29, 2003, entitled "Micro Fuel
Cell."
FIELD OF THE INVENTION
[0002] The present invention generally relates to the field of fuel
cells, and more particularly, to micro fuel cells and methods of
making the same.
BACKGROUND OF THE INVENTION
[0003] A fuel cell produces electrical energy by electrochemically
oxidizing a fuel such as hydrogen or methanol in the cell to
directly convert the chemical energy of the fuel into electrical
energy. Fuel cells have recently drawn attention as a clean supply
source for electrical energy.
[0004] Powering of portable and/or wireless electronic devices is a
significant issue in today's marketplace. While the speed and
functionality of many wireless sensors and/or portable
telecommunications and computing devices tend to be limited by the
power sources, the availability of good power sources is lagging
behind development of the electronic devices themselves. Thus,
improved power supply and management is constantly being
sought.
[0005] A number of miniature fuel cells suitable for use with
electronic products are becoming available today, but less
attention has been shown to the low-cost mass production and device
packaging of these fuel cells for varied applications. There is
limited information in the literature concerning such things as the
methods for manufacturing the fuel cells in a low-cost and
efficient manner.
SUMMARY OF THE INVENTION
[0006] The present invention generally relates to a fuel cell, fuel
cell array and methods of forming the same. In one illustrative
embodiment, a fuel cell is made by forming a first aperture defined
by a first aperture surface through a first electrode layer and
forming a second aperture defined by a second aperture surface
through a second electrode layer. A proton exchange membrane is
then laminated between the first electrode layer and the second
electrode layer, with the proton exchange membrane spanning the
first aperture and the second aperture. A plurality of fuel cells
may also be made in a similar manner, as further described
below.
[0007] In some embodiments, and to help promote adhesion between
the first electrode layer, the second electrode layer and the
proton exchange membrane, an adhesive may be provided between the
electrode layers and the proton exchange membrane. Depending on the
method of making the fuel cells, the apertures can be formed before
or after the adhesive is provided.
[0008] In some embodiments, the first electrode layer and/or the
second electrode layer may include a conductive substrate, while in
other embodiments, the first electrode layer and/or the second
electrode layer may include a non-conductive substrate with a
conductive layer applied to at least a portion thereof. When a
conductive layer is applied, the conductive layer may be patterned
to form one or more fuel cell electrical contacts. In some cases,
the electrical contacts may extend from adjacent the proton
exchange membrane near the apertures to a region that is beyond the
extent of the proton exchange membrane. When such electrical
contacts are provided on both the first electrode layer and the
second electrode layer, at least some of the electrical contacts on
the first electrode layer may become electrically connected to at
least some of the electrical contacts on the second electrode
layer, when the first electrode layer and the second electrode
layer are laminated together. By appropriately patterning the
electrical contacts on the first and second electrode layers, two
or more fuel cells may be electrically connected in series, in
parallel or some combination thereof to provide the desired
electrical output characteristics.
[0009] A plurality of fuel cells can be formed by using any number
of methods disclosed therein. For example, the first electrode
layer and the second electrode layer may include many apertures,
each defining a fuel cell. When a proton exchange membrane is
laminated between the first electrode layer and the second
electrode layer, a plurality of fuel cells may be made. The
plurality of fuel cells can then be diced into single fuel cells or
fuel cell arrays, as desired. In another illustrative embodiment, a
first length of material having a first plurality apertures and a
first plurality of electrical contacts may be moved with a second
length of material having a second plurality apertures and a second
plurality of electrical contacts into a joining unit with a proton
exchange membrane therebetween. The second plurality of apertures
are preferably in registration with the first plurality of
apertures. Once joined, the resulting plurality of fuel cells can
be diced into single fuel cells or fuel cell arrays, as desired
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The invention may be more completely understood in
consideration of the following detailed description of various
embodiments of the invention in connection with the accompanying
drawings, in which:
[0011] FIG. 1A-1D are cross-sectional schematic views of an
illustrative micro fuel cell at various steps of during
manufacture;
[0012] FIG. 1E is a top schematic view of the micro fuel cell shown
in FIG. 1D;
[0013] FIG. 2A-2D are cross-sectional schematic views of another
illustrative micro fuel cell at various steps of during
manufacture;
[0014] FIG. 2E is a top schematic view of the micro fuel cell shown
in FIG. 2D;
[0015] FIG. 3A-3C are cross-sectional schematic views of another
illustrative micro fuel cell at various steps of during
manufacture;
[0016] FIG. 3D is a top schematic view of the micro fuel cell shown
in FIG. 3C;
[0017] FIG. 4A-4C are cross-sectional schematic views of another
illustrative micro fuel cell at various steps of during
manufacture;
[0018] FIG. 4D is a top schematic view of the micro fuel cell shown
in FIG. 4C;
[0019] FIG. 5 is a perspective view of an array of micro fuel
cells;
[0020] FIG. 6 is a perspective view of the array of fuel cells
shown in FIG. 5 diced into various forms;
[0021] FIG. 7 is an exploded perspective view of an array of fuel
cells in accordance with another illustrative embodiment of the
invention;
[0022] FIG. 8 is a schematic side elevation view of an illustrative
method of making the micro fuel cells; and
[0023] FIG. 9 is a perspective view of an illustrative fuel cell
mounted to a fuel reservoir.
[0024] While the invention is amenable to various modifications and
alternative forms, specifics thereof have been shown by way of
example in the drawings and will be described in detail. It should
be understood, however, that the intention is not to limit the
invention to the particular illustrative embodiments described. On
the contrary, the intention is to cover all modifications,
equivalents, and alternatives falling within the spirit and scope
of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0025] The following description should be read with reference to
the drawings, in which like elements in different drawings are
numbered in like fashion. The drawings, which are not necessarily
to scale, depict selected embodiments and are not intended to limit
the scope of the invention. Although examples of construction,
dimensions, and materials may be illustrated for the various
elements, those skilled in the art will recognize that many of the
examples provided have suitable alternatives that may be
utilized.
[0026] The present invention is applicable for use with all
devices, and in particular, those devices that can use small sized
power sources. In some illustrative embodiments, the present
invention provides electrical power using hydrogen and oxygen as a
fuel source. While the present invention is not so limited, an
appreciation of various aspects of the invention will be gained
through a discussion of the various illustrative embodiments and
examples provided below.
[0027] FIG. 1A-1D are cross-sectional schematic views of an
illustrative micro fuel cell at various steps of manufacture. In
FIG. 1A, an electrode 110 has a top surface 112, a bottom surface
114 and a thickness T.sub.1 defined by the distance between the top
surface 112 and the bottom surface 114. In the illustrative
embodiment, a substrate 115, which may be a non-conductive
substrate, is coated with a conductive material 116 on at least a
portion of the top surface and at least a portion of the bottom
surface 114. The conductive material 116 can have any useful
thickness, such as, for example, a thickness of up to 1000
Angstroms or more, as desired. Optional feed-through contacts 117
are also shown electrically connecting the conductive material 116
on the top surface 112 with the conductive material 116 on the
bottom surface 114. In an illustrative embodiment, the electrode
110 can have any useful thickness such as, for example, a thickness
of 2 mil or less. In some embodiments, the conductive material 116
may be patterned to form one or more electrical contacts or pads.
Patterning the conductive material 116 may, for example, help
electrically isolate adjacent fuel cells when a number of fuel
cells are formed simultaneously.
[0028] In FIG. 1B, an optional adhesive layer 120 can be disposed
on the electrode 110. The adhesive layer 120 may be conductive and
can be disposed using conventional methods. The adhesive layer 120
can have any useful thickness, and like the conductive material 116
above, may be patterned in some embodiments, as desired.
[0029] In FIG. 1C, an aperture 135 is formed through the electrode
110 thickness T.sub.1. The aperture 135 can be formed using
conventional methods such as, for example, punching, etching, or
laser cutting. The aperture 135 is defined by an aperture surface
130 surround the aperture 135. The aperture 135 can be any size or
shape. In one illustrative embodiment, the aperture 135 is
rectangular, square, or round and has a cross-sectional surface
area of less than 1 mm.sup.2. However, other shapes and sizes may
also be used, as desired. In FIG. 1A-1C, the adhesive 120 is shown
as being applied before the aperture 135 is formed. However, in
other embodiments, the adhesive 120 may be applied after the
aperture 135 is formed.
[0030] FIG. 1D shows a proton exchange membrane 140 laminated
between a first electrode 110A and a second electrode 110B. The
first electrode 110A and the second electrode 110B can be similar
to the electrode 110 described above. The proton exchange membrane
140 may be any suitable material that allows ions to conduct across
it. Forming the proton exchange membrane encompasses in situ
techniques such as spin or solution casting, as well as providing a
preformed film onto a catalyst. An illustrative commercially
available proton exchange membrane is Nafion.RTM., sold by Dupont
(a perfluorosulfuric acid membrane with a polytetrafluoroethylene
backbone). Other proton exchange membranes are commercially
available, and are known to those skilled in the art. In a
preferred embodiment, the proton exchange membrane can have a
thickness ranging from 10 to 50 micrometers. However, other
thicknesses may be used, if desired. The proton exchange membrane
140 can further include a top and bottom catalyst layer such as,
for example, a carbon/platinum layer adjacent the proton exchange
membrane 140.
[0031] In the illustrative embodiment, the adhesive layer 120 is
disposed between the proton exchange membrane 140 and the first
electrode 110A, and between the proton exchange membrane 140 and
the second electrode 110B. The aperture of the first electrode 110A
is aligned with the aperture of the second electrode 110B, thereby
forming a fuel cell 100. While perfect alignment between the
aperture of the first electrode 110A and the aperture of the second
electrode 110B is not required, the aperture of the first electrode
110A is preferably at least partially aligned with the aperture of
the second electrode 110B.
[0032] The illustrative fuel cell 100 operates as follows. Fuel,
e.g., hydrogen or methanol, is introduced into the aperture 135 in
the first electrode 110A and it diffuses to the first catalyst
layer on the proton exchange membrane 140 first electrode side
110A. The first catalyst layer promotes removal of electrons (for
hydrogen fuel) according to the relationship: ##STR1##
[0033] For methanol, the relationship is: ##STR2##
[0034] The electrons flow from the first catalyst layer through the
conductive material 116 on the first electrode 110A and through an
external circuit (not shown), while the hydrogen ions (i.e.,
protons) move across the proton exchange membrane 140 toward the
second catalyst layer on the proton exchange membrane 140 second
electrode side 110B.
[0035] An oxidant, e.g., air or oxygen, is directed into the second
electrode 110B aperture 135 and diffuses to the second catalyst
layer on the proton exchange membrane 140. At this second catalyst
layer, oxygen from the oxidant reacts both with the hydrogen ions
flowing across the membrane 140 and with the electrons flowing to
the second catalyst layer from the external circuit to form water,
according to the relationship: ##STR3##
[0036] The electron flow provides the desired current, and the
water by-product is removed from the cell, often by evaporation.
FIG. 1E is a top schematic view of the illustrative embodiment of a
micro fuel cell 100 shown in FIG. 1D.
[0037] FIG. 2A-2D are cross-sectional schematic views of another
illustrative micro fuel cell at various steps of manufacture. In
FIG. 2A, an electrode 210 has a top surface 212, a bottom surface
214 and a thickness T.sub.2 defined by the distance between the top
surface 212 and the bottom surface 214. In the illustrative
embodiment, the electrode 210 is a conductive material such as, for
example, a conductive metal or conductive polymer. In an
illustrative embodiment, the electrode 210 can have any useful
thickness such as, for example, a thickness of 2 mil or less.
However, other thicknesses may also be used.
[0038] In FIG. 2B, an optional adhesive layer 220 can be disposed
on the electrode 210. The adhesive layer 220 may be conductive and
can be disposed using conventional methods. The adhesive layer 220
can have any useful thickness.
[0039] In FIG. 2C, an aperture 235 can be formed through the
electrode 210 thickness T.sub.2. The aperture 235 can be formed
using conventional methods such as, for example, punching, etching,
or laser cutting. The aperture 235 is defined by an aperture
surface 230 surrounding the aperture 235. The aperture 235 can be
any useful size or shape. In an illustrative embodiment, the
aperture 235 is rectangular, square, or round and has a
cross-sectional surface area of less than 1 mm.sup.2. In FIG.
2A-2C, the adhesive 220 is shown as being applied before the
aperture 235 is formed. However, in other embodiments, the adhesive
220 may be applied after the aperture 235 is formed.
[0040] FIG. 2D shows a proton exchange membrane 240 laminated
between a first electrode 210A and a second electrode 210B. The
first electrode 210A and the second electrode 210B can be similar
to the electrode 210 described above. In the illustrative
embodiment, the adhesive layer 220 is disposed between the proton
exchange membrane 240 and the first electrode 210A, and between the
proton exchange membrane 240 and the second electrode 210B. Like
above, the aperture of the first electrode 210A is at least
partially aligned with the aperture of the second electrode 210B.
The completed assembly forms a fuel cell 200. The proton exchange
membrane 240 can further include a top and bottom catalyst layer
adjacent the proton exchange membrane 240, as described above. FIG.
2E is a top schematic view of the illustrative embodiment of a
micro fuel cell 200 shown in FIG. 2D.
[0041] FIG. 3A-3D are cross-sectional schematic views of another
illustrative micro fuel cell at various steps during manufacture.
In FIG. 3A, an electrode 310 has a top surface 312, a bottom
surface 314 and a thickness T.sub.3 defined by the distance between
the top surface 312 and the bottom surface 314. In the illustrative
embodiment, the electrode 310 is a conductive material such as, for
example, a conductive metal or conductive polymer. In an
illustrative embodiment, the electrode 310 can have any useful
thickness such as, for example, a thickness of 2 mil or less.
[0042] In the illustrative embodiment, an aperture 335 can be
pre-formed through the electrode 310 thickness T.sub.3. The
aperture 335 can be formed using conventional methods such as, for
example, punching, etching, or laser cutting. The aperture 335 is
defined by an aperture surface 330 surrounding the aperture 335.
The aperture 335 can be any useful size or shape. In an
illustrative embodiment, the aperture 335 is rectangular, square,
or round and has a cross-sectional surface area of less than 1
mm.sup.2.
[0043] In FIG. 3B, an optional adhesive layer 320 can be disposed
on the electrode 310. The adhesive layer 320 may be conductive and
may be disposed using conventional methods. The adhesive layer 320
can have any useful thickness. In FIG. 3A-3C, the adhesive 320 is
shown as being applied after the aperture 335 is formed. However,
in other embodiments, the adhesive 320 may be applied before the
aperture 335 is formed.
[0044] FIG. 3C shows a proton exchange membrane 340 laminated
between a first electrode 310A and a second electrode 310B. The
first electrode 310A and the second electrode 310B can be similar
to the electrode 310 described above. In the illustrative
embodiment, the adhesive layer 320 is disposed between the proton
exchange membrane 340 and the first electrode 310A, and between the
proton exchange membrane 340 and the second electrode 310B. The
aperture of the first electrode 310A is at least partially aligned
with the aperture of the second electrode 310B. The completed
assembly forms a fuel cell 300. The proton exchange membrane 340
can further include a top and bottom catalyst layer adjacent the
proton exchange membrane 340, as described above. FIG. 3D is a top
schematic view of the illustrative embodiment of a micro fuel cell
300 shown in FIG. 3C.
[0045] FIG. 4A-4D are cross-sectional schematic views of another
illustrative micro fuel cell at various steps of during
manufacture. In FIG. 4A, an electrode 410 has a top surface 412, a
bottom surface 414 and a thickness T.sub.4 defined by the distance
between the top surface 412 and the bottom surface 414. In the
illustrative embodiment, the electrode 410 includes a
non-conductive material or substrate 415. In an illustrative
embodiment, the electrode 410 can have any useful thickness such
as, for example, a thickness of 2 mil or less.
[0046] In the illustrative embodiment, an aperture 435 is
pre-formed through the electrode 410 thickness T.sub.4. The
aperture 435 can be formed using conventional methods such as, for
example, punching, etching, or laser cutting. The aperture 435 is
defined by an aperture surface 430 surrounding the aperture 435.
The aperture 435 can be any useful size or shape. In an
illustrative embodiment, the aperture 435 is rectangular, square,
or round and has a cross-sectional surface area of less than 1
mm.sup.2.
[0047] In the illustrative embodiment of FIG. 4A, the substrate 415
is coated with a conductive material 416 on at least a portion of,
or the entire aperture surface 430. In addition, the conductive
material can be disposed on at least a portion of the top surface
412 and/or at least a portion of the bottom surface 414. In some
embodiments, the conductive material may be patterned on the top
surface 412 and/or the bottom surface 414. The conductive material
116 on the aperture surface 430 may provide a seal that helps
prevent the fuel from escaping from the aperture 435, particularly
if the substrate 415 is somewhat porous to the fuel source. In an
illustrative embodiment, the conductive material 116 can have any
useful thickness, such as, for example, a thickness of up to 1000
Angstroms. The conductive material 116 can be a conductive metal or
conductive polymer, for example.
[0048] In FIG. 4B an optional adhesive layer 420 can be disposed on
the electrode 410. The adhesive layer 420 may be conductive and can
be disposed using conventional methods. The adhesive layer 420 can
have any useful thickness. In some cases, the aperture is formed
after the adhesive is applied, while in others it is formed before
the adhesive is applied.
[0049] FIG. 4C shows a proton exchange membrane 440 laminated
between a first electrode 410A and a second electrode 410B. The
first electrode 410A and the second electrode 410B can be similar
to the electrode 410 described above. In the illustrative
embodiment, the adhesive layer 420 is disposed between the proton
exchange membrane 440 and the first electrode 410A, and between the
proton exchange membrane 440 and the second electrode 410B. Like
above, the aperture of the first electrode 410A is at least
partially aligned with the aperture of the second electrode 410B.
The completed assembly forms a fuel cell 400. The proton exchange
membrane 440 can further include a top and bottom catalyst layer
adjacent the proton exchange membrane 440, as described above. FIG.
4D is a top schematic view of the illustrative embodiment of a
micro fuel cell 400 shown in FIG. 4C.
[0050] FIG. 5 is a perspective view of an array of micro fuel
cells. In some illustrative embodiments, a plurality of micro fuel
cells 500 can be economically produced on a large sheet 501 of
material. The sheet 510 can include a plurality of apertures 535
through a top electrode 510A and a bottom electrode 510B, as
described above. Each aperture has an aperture cross-sectional
surface area 530, as described above. A proton exchange membrane
540 can be disposed between the top electrode 510A and the bottom
electrode 510B, preferably spanning the apertures so as to become
exposed to a fuel source.
[0051] FIG. 6 is a perspective view of an array of fuel cells 600
shown in FIG. 5, diced into various forms. The sheet 501 of FIG. 5
can be divided into single fuel cells, or a plurality of fuel cell
arrays. In some cases, the fuel cells in a fuel cell array can be
connected in series, in parallel, or some combination thereof,
depending on the application. Connecting the fuels cells in series
will tend to increase the output voltage level, while connecting
the fuel cells in parallel with tend to increase the output current
level. Thus, by appropriately connecting the fuel cells in parallel
and/or series, desired electrical output characteristics of the
fuel cell can be achieved. In one illustrative embodiment, each
fuel cell array can have five or more fuel cells electrically
connected in series.
[0052] FIG. 7 is an exploded perspective view of an array of fuel
cells 700 in accordance with an illustrative embodiment of the
invention. In the illustrative embodiment, a top electrode 710A has
a plurality of apertures 735A and a bottom electrode 710B has a
plurality of apertures 735B. The apertures 735A and 735B are shown
at least partially aligned with a proton exchange membrane 740
disposed between the top electrode 710A and the bottom electrode
710B. The proton exchange membrane 740 is shown spanning the
apertures 735A and 735B and extending along a proton exchange
membrane (PEM) region 745A and 745B.
[0053] Electrical contacts 750A extend away from the apertures 735A
on the top electrode 710A to a first region 755A. Electrical
contacts 750B extend away from the apertures 735B on the bottom
electrode 710B to a first region 755B. At least one electrical
contact 750A on the top electrode 710A at least partially overlaps
an electrical contact 750B on the bottom electrode 710B in an
overlap region 760A and 760B. In the illustrative embodiment, the
proton exchange membrane 740 does not extend out between the top
electrode 710A or bottom electrode 710B in the overlap region 760A
and 760B. Thus, when the top electrode 710A is laminated to the
bottom electrode, with the proton exchange membrane 740 disposed
therebetween, the electrical contact 750A on the top electrode 710A
may become electrically connected to the electrical contact 750B on
the bottom electrode 710B. This may electrically connect one micro
fuel cell in series with another micro fuel cell. Similar methods
may be used to electrically connect micro fuel cells in parallel,
and/or in series and in parallel, as desired.
[0054] FIG. 8 is a schematic side elevation view of an illustrative
method of making the micro fuel cells. In the illustrative
embodiment, an array of fuel cells 800 can be formed on a
continuous sheet at shown in FIG. 5 in a roll to roll process. A
continuous length of top electrode 710A can be provided on a first
roll 705A. For example, a continuous length of bottom electrode
710B can be provided on a second roll 705B. The continuous length
of top electrode 710A and bottom electrode 710B can be simultaneous
moved into a joining unit 880 with a continuous length of proton
exchange membrane 840 between the continuous length of top
electrode 710A and bottom electrode 710B. Apertures can be
pre-formed or formed just prior to entering the joining unit 880.
The apertures in the top electrode 710A and bottom electrode 710B
are in at least partial registration prior to entering the joining
unit 880. The joining unit 880 can be any conventional laminating
operation that applies pressure to the top electrode 810A and
bottom electrode 810B to form a fuel cell laminate described
herein. When an adhesive is to be used, the adhesive can be applied
to the proton exchange membrane and/or the top electrode 710A and
bottom electrode 710B prior to entering the joining unit 880. After
exiting the joining unit 880, a dicer may be provided for dicing
the plurality of fuel cells into single fuel cells or fuel cell
arrays, if desired.
[0055] FIG. 9 is a perspective view of an illustrative fuel cell
900 mounted to a fuel reservoir 909. In the illustrative
embodiment, a fuel cell array 900 is fixed to the reservoir 909
such that the proton exchange membrane is exposed through the
apertures to the fuel in the reservoir 909. The reservoir 909 can
contain a fuel source such as hydrogen or the like. The fuel cell
array 900 may include electrical contacts 912A and 912B, which may
represent two or more fuel cells connected in series, parallel or
some combination thereof. The electrical contacts 912A and 912B may
be used to provide power to an external load. In this embodiment,
the byproduct is water, which collects on the outer surface of the
proton exchange membrane, and evaporates into the surrounding
air.
[0056] The present invention should not be considered limited to
the particular examples described above, but rather should be
understood to cover all aspects of the invention as fairly set out
in the attached claims. Various modifications, equivalent
processes, as well as numerous structures to which the present
invention can be applicable will be readily apparent to those of
skill in the art to which the present invention is directed upon
review of the instant specification.
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