Continuum simulation is employed to study ion transport and fluid flowthrough a nanopore in a solid-state membrane under an applied potential drop.Results show the existence of concentration polarization layers on the surfacesof the membrane. The nonuniformity of the ionic distribution gives rise to anelectric pressure that drives vortical motion in the fluid. There is also a nethydrodynamic flow through the nanopore due to an asymmetry induced by themembrane surface charge. The qualitative behavior is similar to that observedin a previous study using molecular dynamic simulations. The current--voltagecharacteristics show some nonlinear features but are not greatly affected bythe hydrodynamic flow in the parameter regime studied. In the limit of thinDebye layers, the electric resistance of the system can be characterized usingan equivalent circuit with lumped parameters. Generation of vorticity can beunderstood qualitatively from elementary considerations of the Maxwellstresses. However, the flow strength is a strongly nonlinear function of theapplied field. Combination of electrophoretic and hydrodynamic effects can leadto ion selectivity in terms of valences and this could have some practicalapplications in separations.
展开▼
