Enhanced mixing in 2D micro-channel electro-osmotic flows

Micro electro-mechanical system (MEMS) elements are extremely small, so slow mixing due to low Reynolds number is the one of most significant performance limitations for micro-fluidic systems. The present work is a numerical study of the electro-osmotic flows (EOF) in micro-channel with non-uniform wall zeta potential. In particular, the mixing enhancements of micro-channel flow were investigated, which are due to induced transverse flows resulting from the variations in the wall zeta potential. Based on the Helmholtz-Smoluchowski wall slip velocity model for EOF, four cases of electro-osmotic flows in micro-channel with non-uniform wall slip velocity and the mixing of the passive scale in these flows were computed with the semi-implicit method for pressure-linked equations (SIMPLE) algorithm. The results show that the non-uniform wall slip velocity induce zigzag streamlines, and as a result, the mixing are enhanced. In generally, the mixing efficiency increases with the strength of the transverse flows.