Method for enhancing current throughput in an electrochemical system
An electrochemical system with reduced limiting-current behavior is disclosed. The electrochemical system is useful for fuel cells and bio-sensors. In part, the invention relates a method of reducing or eliminating limiting-current behavior in the operation electrochemical systems, in particular those with ion-selective membrane or electrochemical electrodes, by spatially reducing the convection near the membrane or the electrode. The invention further relates to electrochemical systems in which micropores, microarrays or pillar arrays are used to reduce convection in comparison to conventional systems without microarrays, micropores or pillar arrays.
1. An electrochemical system comprising a substrate, a plurality of microchannels fabricated onto said substrate, a plurality of electrodes in fluid communication with said microchannels and distal to the nanojunction, and a nanojunction connecting at least two of said microchannels wherein at least a part of said substrate contains a microarray, micropore array or a pillar array proximal to the nanojunction.
2. The system of claim 1 , wherein when said microchannels contain a fluid and a current is applied, convection currents near said nanojunction are reduced when compared to convection currents near a nanojunction of same type electrochemical system without a pillar array or micropore array.
3. The electrochemical system of claim 1 , further comprising an ion-selective membrane between said microchannels.
4. The electrochemical system of claim 1 , comprising a Nafion membrane.
5. The electrochemical system of claim 1 , comprising a pillar array wherein the average diameter of pillar is between about 0.1-1000 μm.
6. The electrochemical system of claim 5 , comprising a pillar array wherein the average pillar height is between about 1-1000 μm.
7. The electrochemical system of claim 5 , comprising a pillar array wherein the average pillar height is between about 1-500 μm.
8. The electrochemical system of claim 5 , comprising a pillar array wherein the average pillar height is between about 1-250 μm.
9. The electrochemical system of claim 5 , comprising a pillar array wherein the average pillar height is between about 5-100 μm.
10. The electrochemical system of claim 5 , comprising a pillar array wherein the average pillar height is between about 5-50 μm.
11. The electrochemical system of claim 5 , comprising a pillar array wherein the average pillar height is between about 5-25 μm.
12. The electrochemical system of claim 1 , comprising a pillar array wherein the average diameter of pillar is between about 1-100 μm.
13. The electrochemical system of claim 1 , comprising a pillar array wherein the average diameter of pillar is between about 5-50 μm.
14. The electrochemical system of claim 1 , comprising a pillar array wherein the average diameter of pillar is between about 7-15 μm.
15. The electrochemical system of claim 1 , comprising a pore array wherein the average diameter of the pores is between about 0.1-500 μm.
16. The electrochemical system of claim 15 , comprising a pore array wherein the pore depth is between about 1-250 μm.
17. The electrochemical system of claim 15 , comprising a pore array wherein the pore depth is between about 2-200 μm.
18. The electrochemical system of claim 15 , comprising a pore array wherein the pore depth is between about 5-100 μm.
19. The electrochemical system of claim 1 , comprising a pore array wherein the average diameter of the pores is between about 1-50 μm.
20. The electrochemical system of claim 1 , comprising a pore array wherein the average diameter of the pores is between about 2-25 μm.
21. The electrochemical system of claim 1 , wherein said substrate is polydimethylsiloxane.
22. The electrochemical system of claim 1 , wherein said pillar array is polydimethylsiloxane.
23. A method of reducing limiting current behavior across an ion-selective membrane in an electrochemical system comprising providing a fabricated non-planar structure on at least one side of the membrane wherein convection near said membrane is reduced in comparison to having planar structures on both sides of the membrane.
24. The method according to claim 23 , wherein said non-planar structure is a micro-array.
25. The method according to claim 23 , wherein said non-planar structure is a pillar array.
26. The method according to claim 23 , wherein said non-planar structure is a pillar micro-array.
27. The method according to claim 23 , wherein said non-planar structure has a microchannel.
28. The method according to claim 27 , wherein said microchannel is curved.
29. The method according to claim 27 , wherein said microchannel has a parabolic shape.
30. The method according to claim 29 , wherein said microchannel has a locus near a nanochannel.
31. An electrochemical system comprising a substrate, a plurality of fluidic channels fabricated on said substrate, wherein at least two separate fluidic channels are connected by a junction, a plurality of electrodes in fluid communication with said fluidic channels, wherein at least one part of said substrate contains a pillar array.
32. The electrochemical system of claim 31 , wherein said fluidic channels are microchannels.
33. The electrochemical system of claim 31 , wherein said junction is a nanojunction.
34. The electrochemical system of claim 31 , wherein said junction comprises an ion-selective membrane.
35. An electrochemical system comprising an electrode seated in a reservoir, a pillar array placed over and in proximity to, but separate from, said electrode, an electrolyte, a substrate, and a support, wherein said substrate comprises one or more microchannels.
36. The electrochemical system of claim 35 wherein the pillar array is suspended over the electrode.
37. The electrochemical system of claim 36 , comprising a pillar array wherein the average diameter of pillar is between about 0.1-1000 μm.
38. The electrochemical system of claim 36 , comprising a pillar array wherein the average diameter of pillar is between about 1-100 μm.
39. The electrochemical system of claim 36 , comprising a pillar array wherein the average diameter of pillar is between about 5-50 μm.
40. The electrochemical system of claim 36 , comprising a pillar array wherein the average diameter of pillar is between about 7-15 μm.