Electroosmotic Micromixing in Physicochemically Patterned Microchannels

The study computationally explores the possibilities of vortex generation and micromixing inside a physicochemically patterned serpentine microchannel wherein a weak electrolyte is undergoing an electroosmotic flow. The results highlight the inefficiency of such serpentine microchannels in the absence of chemical patches due to the development of periodic electroosmotic and pressure-driven flows in the direction normal to the applied electric field. The periodic chemical patches with positive and negative ζ-potentials decorated on the microchannel walls facilitate reverse flow to enable the formation of an array of counter-rotating vortices inside the microchannel. While the rotational direction of the vortices could be periodically adjusted using an alternating field, the usage of channels with obtuse angles showed potential for uniform electroosmotic flow all along the serpentine channel. The number, size, and strength of vortices and mixing efficiency have been correlated with the number of chemical patches, ζ-potential gradients, and the effects of filleted edges, among other parameters.