Overlimiting current in a microchannel

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 con...

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Bibliographic Details
Published in:Physical review letters 2011-09, Vol.107 (11), p.118301-118301, Article 118301
Main Authors: Dydek, E Victoria, Zaltzman, Boris, Rubinstein, Isaak, Deng, D S, Mani, Ali, Bazant, Martin Z
Format: Article
Language:English
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Summary: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.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.107.118301