Mixing enhancement in a microchannel through electrochemical method. Top figure shows the oscillating potential and bottom figure shows the moving particles in the bulk. The dimension of the microchannel is 200 microns x 400 microns, which is typical for microfluidic devices. An electrode is placed at the upper-right corner of the microchannel. By changing the potential on the electrode, we can oxidize or reduce the redox-active surfactants that are distributed on the channel top surface and surface tension gradients are generated. The bulk fluids go through a stretched/refolded process at each potential oscillating period. The stretching/refolding will drive a chaos in the bulk and dramatically enhance the mixing.