MEMS-based fuel cell and methods
View Patent ↗A fuel cell has a MEMS fuel-cell structure including an anode, a cathode, and an electrolyte, formed on a substrate, a portion of the substrate being removed from beneath the MEMS structure to leave the MEMS structure suspended in membrane form. An opening may extend through the substrate to leave the MEMS fuel-cell structure in a cantilevered configuration, supported by only one edge. Additional openings may be formed to relieve mechanical stress near an edge or edges supporting the MEMS fuel-cell structure, and/or to limit heat-conducting paths. Specially adapted methods are disclosed for fabricating the MEMS-based fuel cell in any of its various configurations.
1. A fuel cell comprising:
a substrate having a substrate top surface, a substrate bottom surface, and an opening, said opening extending upward from said substrate bottom surface; and
a MEMS structure at least partially aligned with said opening, said MEMS structure including a first portion disposed on said substrate top surface and a second portion extending over only part of said opening, whereby said second portion of said MEMS structure forms a cantilever supported only by said first portion of said MEMS structure, said MEMS structure comprising an anode, a cathode, and an electrolyte in contact with said anode and cathode.
2. The fuel cell of claim 1 , wherein at least a portion of said opening extends through said substrate.
3. The fuel cell of claim 1 , wherein said cantilever comprises a salient portion of said substrate.
4. The fuel cell of claim 3 , wherein said salient portion of said substrate supports the anode, cathode, and electrolyte of the fuel cell.
5. The fuel cell of claim 3 , wherein said salient portion of said substrate includes openings extending through said salient portion.
6. The fuel cell of claim 3 , wherein said salient portion of said substrate is porous.
7. The fuel cell of claim 1 , wherein at least one element selected from said anode, cathode, and electrolyte extends over both said first and second portions of said MEMS structure.
8. The fuel cell of claim 7 , wherein said at least one element extending over both of said first and second portions of said MEMS structure supports the remaining elements of said electrolyte, anode, and cathode.
9. The fuel cell of claim 7 , wherein said at least one element extending over both of said first and second portions of said MEMS structure is the anode.
10. The fuel cell of claim 7 , wherein said at least one element extending over both of said first and second portions of said MEMS structure is the cathode.
11. The fuel cell of claim 7 , wherein said at least one element extending over both of said first and second portions of said MEMS structure is the electrolyte.
12. The fuel cell of claim 7 , wherein said at least one element extending over both of said first and second portions of said MEMS structure comprises at least two elements selected from said, anode, cathode, and electrolyte.
13. The fuel cell of claim 1 , wherein said MEMS structure comprises a stack of layers, said layers including said electrolyte, anode, and cathode.
14. The fuel cell of claim 1 , wherein said MEMS structure comprises a cathode layer supported by an electrolyte layer, said electrolyte layer being supported in turn by an anode layer.
15. The fuel cell of claim 1 , wherein said MEMS structure comprises an anode layer supported by an electrolyte layer, said electrolyte layer being supported in turn by a cathode layer.
16. The fuel cell of claim 1 , wherein both said cathode and anode are supported by a solid electrolyte layer.
17. The fuel cell of claim 16 , wherein said cathode comprises a patterned thin film in contact with said solid electrolyte layer.
18. The fuel cell of claim 16 , wherein said anode comprises a patterned thin film in contact with said solid electrolyte layer.
19. The fuel cell of claim 16 , wherein both said anode and cathode comprise patterned thin films in contact with said solid electrolyte layer.
20. The fuel cell of claim 16 , wherein each of said anode and said cathode comprises a thin film in contact with opposite sides of said solid electrolyte layer.
21. The fuel cell of claim 16 , wherein each of said anode and said cathode comprises a patterned thin film in contact with the same side of said solid electrolyte layer, said anode and cathode being spaced apart from each other.
22. The fuel cell of claim 21 , wherein said anode and said cathode are suitably patterned to interleave with each other.
23. A fuel cell comprising:
a substrate having a substrate top surface, a substrate bottom surface, and an opening, said opening extending upward from said substrate bottom surface; and a MEMS structure at least partially aligned with said opening, said MEMS structure including a first portion disposed on said substrate top surface and a second portion extending over only part of said opening, whereby said second portion of said MEMS structure forms a cantilever supported only by said first portion of said MEMS structure, said MEMS structure comprising an anode, a cathode, and an electrolyte in contact with said anode and cathode, the fuel cell further comprising a mechanical stress-relief feature, said stress-relief feature comprising at least a second opening contiguous with both of said first and second portions of said MEMS structure.
24. The fuel cell of claim 23 , wherein said at least second opening of said stress-relief feature extends downward from said substrate top surface.
25. The fuel cell of claim 23 , wherein said at least second opening of said stress-relief feature extends through said substrate.
26. The fuel cell of claim 23 , wherein said at least second opening of stress-relief feature comprises an opening elongated in a direction parallel to said substrate top surface.
27. The fuel cell of claim 23 , wherein said stress-relief feature comprises a series of openings extending through said substrate, each opening of said series of openings being disposed contiguous with said second portion of said MEMS structure.
28. An electronic device comprising the fuel cell of claim 1 .
29. A fuel cell comprising:
a substrate having a substrate top surface, a substrate bottom surface, and an opening, said opening extending upward from said substrate bottom surface; and
a MEMS structure at least partially aligned with said opening, said MEMS structure including a first portion disposed on said substrate top surface and a second portion extending cantilevered over only part of said opening, said second portion of said MEMS structure comprising a patterned thin film anode, a patterned thin film cathode, and a solid electrolyte in contact with said patterned thin film anode and cathode.
30. The fuel cell of claim 29 , wherein said substrate comprises a material suitably stable at a desired temperature of operation, said material being selected from the list consisting of semiconductors, metals, oxides, ceramics, plastics, and solid polymers.
31. The fuel cell of claim 29 , wherein said substrate comprises silicon.
32. An electrical energy source comprising in combination:
a MEMS structure, said MEMS structure comprising means for producing electrical current in an electrolyte for delivering said electrical energy;
means for supporting said MEMS structure; and
means for cantilevering said MEMS structure from said means for supporting said MEMS structure.
33. The electrical energy source of claim 32 , wherein said electrical-current-producing means includes an anode, a cathode, and said electrolyte disposed in contact with said anode and cathode.
34. The electrical energy source of claim 32 , further comprising means for conducting heat away from said electrical-current-producing means.
35. A fuel cell comprising in combination:
a substrate having a substrate top surface, a substrate bottom surface, and an opening, said opening extending upward from said substrate bottom surface; and
a MEMS structure at least partially aligned with said opening, said MEMS structure including a first portion disposed adjacent to said substrate top surface and a second portion extending over only part of said opening,
said MEMS structure comprising an anode, a cathode, and an electrolyte in contact with said anode and cathode,
said first portion of said MEMS structure having thermal contact with said substrate for conducting away heat generated in said second portion of said MEMS structure and said first portion of said MEMS structure having one or more openings for relief of mechanical stress,
said second portion of said MEMS structure having an edge free to move in response to said generated heat to reduce said mechanical stress.
36. An electronic device comprising the fuel cell of claim 35 .