Efficacy of microconfined fluid mixing in a combined electroosmotic and pressure driven transport of complex fluid over discrete electrodes

Abstract

This paper numerically investigates the mixing characteristics of an Oldroyd-B fluid flowing through a micro-channel having discrete electrodes along its walls driven by both electroosmotic force and pressure gradient. We consider both symmetric and asymmetric potential distributions along the wall while also probing the influence of fluid rheology and other physicochemical parameters of the problem. We report an improvement in mixing efficiency by increasing the relative strength of electroosmotic forcing and pressure gradient. It is also observed that the localized mixing efficiency decreases with an increase in surface potential. Fluid rheology changes the position of maximum efficiency depending on fluid properties without affecting mixing efficiency substantially. Compared with a continuous distribution, the five-electrode arrangement produces approximately equivalent mixing efficiency. We observe an increase in mixing efficiency at the micro-channel outlet as the gap between the electrodes increases. We have also analyzed the mixing characteristics for asymmetric charge distributions and illustrated the parameters controlling the flow dynamics. The results of the present study may prove helpful for the complete design and analysis of an active micromixer for the efficient transport of bio/polymeric fluids inside micro-channels.