Pumping and mixing in a microchannel using AC asymmetric electrode arrays

A numerical study of electroosmotic microchannel flow driven by arrays of AC (alternating current) asymmetric electrodes was carried out. By installing asymmetric electrode arrays on the top and bottom walls of the microchannel, pumping and mixing flow modes can be generated. The ‘pumping mode’ (P) is generated when the sequences of asymmetric electrode pairs (narrow to wide) on the top and bottom walls are in phase, whereas the ‘mixing mode’ (M) is generated by switching the sequence of electrode pairs of the top wall (e.g., wide to narrow). By combining mixing and pumping modes, enhanced mixing performance can be achieved without significantly reducing the flow rate. Among various combinations of P and M modes, the alternating PM mode showed the best mixing performance due to the iterative convergent and divergent flow motions. The effects of Peclet number and channel height on the mixing efficiency were analyzed in detail.