An electro-thermal micro mixer

The mixer in the present study is essentially a Y-type micro channel with an electrode array built on the bottom wall of its straight main channel. Electro-thermally driven vortices are generated in the electrolyte above the corners of electrodes by applying ac signals at 6 peak-to-peak volts and 1 MHz with 180° phase shift to each electrode pair of the arrays. The vortices stir the liquid and thus enhance mixing. Experiments were carried out by feeding two equal streams of saline water with different dyes into the mixer for various parameters of electrode array configuration and background flow rates. For a mixing channel with height 30 µm, width 400 µm and length 13 mm, the mixing is enhanced substantially by the vortices even when the background average flow speed is increased up to 972 µm/s. Numerical simulation was carried out for understanding the structure of the vortices and the behind physics.