Effect of complex vortices generated by asymmetrically distributed induced charges on fluid flow and mass transfer in pressure driven micromixers

Abstract

Microscale electric field-induced vortical structures, arising from spatial accumulation of induced charges, demonstrate significant potential for augmenting mixing performance in low Reynolds number (Re) laminar flows. This investigation establishes a computational framework incorporating an asymmetric conductive plate with hybrid linear-curvilinear edges to systematically elucidate the coupling mechanisms between inhomogeneous charge distributions, complex vortex generation, and pressure-driven molecular transport. Our findings reveal that under balanced pressure-driven flow (PDF) and induced-charge electroosmotic flow (EOF), expanding the polarization area promotes bilateral charge accumulation along curvilinear boundaries, creating localized electric field minima that suppress interfacial slip velocity and mixing efficiency. In contrast, linear edges exhibit maximum slip velocities, generating vortex pairs with enhanced convection capacity. Notably, plate reorientation and increased curvature radius amplify surface electric field asymmetry, achieving superior mass transfer through either expanded vortex perturbation domains or intensified rotational intensity. When PDF dominates EOF by 25-fold, the weakened charge heterogeneity minimally stimulates vortex development, rendering interfacial perturbation the primary mixing driver. This work advances fundamental understanding of asymmetric charge-polarization dynamics in microscale flow manipulation, offering critical insights for designing active micromixers.