Wall embedded electrodes to modify electroosmotic flow in silica nanoslits

Abstract

Electroosmotic flow in a silica slit channel with nonuniform surface charge density is investigated. In nanoconfinement, the electrical double layer occupies a non-negligible fraction of the system. Therefore, modifying the charge density on specific locations on the channel wall surface allows effective manipulation of the electroosmotic flow rates. In the present study, extensive (160 ns) nonequilibrium molecular dynamics simulations are conducted to investigate the ability of controlling the electroosmotic flow control in a nanoslit by patterning the surface potential. The mechanism to modify the surface charge consists of a set of charged electrodes embedded within one of the channel walls. The presence of the embedded electrodes results in the redistribution of ions in the electrolyte solution and in the alteration of the electroosmotic flow throughout the nanochannel. Indeed, the results reveal significant changes in the electroosmotic driving force and velocity profiles including local flow reversal. This study provides physical insight into the direct manipulation of the electrokinetic flow in nanoslits.