Overlimiting current in a microchannel |
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Authors: | Dydek E Victoria Zaltzman Boris Rubinstein Isaak Deng D S Mani Ali Bazant Martin Z |
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Affiliation: | Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA. |
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Abstract: | We revisit the classical problem of diffusion-limited ion transport to a membrane (or electrode) by considering the effects of charged sidewalls. Using simple mathematical models and numerical simulations, we identify three basic mechanisms for overlimiting current in a microchannel: (i)?surface conduction carried by excess counterions, which dominates for very thin channels, (ii)?convection by electro-osmotic flow on the sidewalls, which dominates for thicker channels, and (iii) transitions to electro-osmotic instability on the membrane end in very thick channels. These intriguing electrokinetic phenomena may find applications in biological separations, water desalination, and electrochemical energy storage. |
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