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 side walls. Using simple mathematical models and numerical simulations, we identify three basic mechanisms for over-limiting current in a microchannel: (i) {\it surface conduction} carried by excess counterions, which dominates for very thin channels, (ii) convection by {\it electro-osmotic flow} on the side walls, which dominates for thicker channels and transitions to (iii) {\it 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. 
E. Victoria Dydek, Boris Zaltzman, Isaak Rubinstein, D. S. Deng, Ali   Mani, and Martin Z. Bazant
physics.flu-dyn physics.chem-ph