Electrokinetic flow-induced currents in silica nanofluidic channels

Abstract

Electrokinetic flow-induced currents inside slit-shaped silica nanochannels are investigated. The unusual features observed experimentally in silica nanochannels are described successfully using a new theoretical framework. First, a simple and reliable physicochemical boundary condition at the interface between the channel surface and the solution is suggested. It accounts for the surface conduction effect through the Stern layer and the dependence of the surface charge on the salt concentration and pH, which were commonly neglected in previous studies. Second, the proposed boundary condition is then incorporated into the traditional Poisson-Boltzmann and Nernst-Planck models to complete the self-consistent model. Model predictions are validated by comparison with experimental data. It is found that the direct numerical predictions of the concentration polarization and the induced potential or pressure field are possible, and these allow us to describe the dependence of currents on the solution properties in the nanofluiclic channel more accurately than the models Proposed in previous studies. (C) 2009 Elsevier Inc. All rights reserved.