Desalination Shocks and Overlimiting Current in Microstructures Academic Article uri icon


  • The transport of ions in bulk electrolytes is governed by diffusion and convection, but the proximity of a charged surface introduces interfacial effects, notably electro-osmotic flow and surface conduction. In this paper, we describe a class of nonlinear electrokinetic phenomena that results from the competition between bulk and interfacial transport in microstructures. First we consider the fundamental problem of steady state current through a dead-end microchannel with an ion perm-selective surface (membrane or electrode) at the end4. The presence of charged side walls provides two new mechanisms for over-limiting current (exceeding diffusion limitation) in addition to bulk electro-osmotic instability on the membrane, which dominates in thick channels. For very thin channels (< 1micron in water), over-limiting current is carried by surface conduction in the depleted region, and we …

publication date

  • March 1, 2011