Electroosmotic mixing in a microchannel with heterogeneous slip dependent zeta potential

Abstract

We investigate the electroosmotic mixing characteristics for flow through a hydrophobic microchannel with interfacial slip dependent heterogeneous surface charge. A comprehensive theoretical framework is developed to solve the Poisson–Boltzmann equation for the induced potential within the electrical double layer, mass and momentum conservation equations for fluid flow, and species transport equation with appropriate boundary conditions. We identify two different flow regimes based on diffusive Peclet number such that in the first regime the value of mixing efficiency is almost 100% as the recirculation zones formed due to the non-uniform surface potential provide sufficient convection mixing and the flow rate enhances with the slip length. The critical value of Peclet number increases with both the slip length and Debye parameter. In the next regime the effect of interfacial slip is significant in altering the mixing performance and the mixing efficiency decreases both with the slip and Debye parameter. The patch surface potential modulates the flow rate and mixing performance and, in this context, different range of patch surface potential for the considered physicochemical parameters is identified for which both the flow rate and mixing efficiency enhances due to the interfacial slip.