Microfluidic mixing with electrokinetic instability in a double T-shaped microchannel

This paper investigates the EKI phenomenon in a double T-shaped microchannel, in which two aqueous electrolyte solutions with a 3.5:1 conductivity ratio are driven electrokinetically into the mixing channel via the application of a DC electrical field. A stratified flow condition is formed when the intensity of the applied DC electrical field is below a certain threshold value. However, as the intensity is increased the lower high-conductivity stream in the entrance region of the main mixing channel fluctuates alternately in the upward and downward direction resulting in a series of flow circulations forms at the interfaces of neighboring solutions flows, and then propagate in the downstream direction. It is found that the electric perturbations added at upper inlet of the microchannel near the main mixing channel can stir the microfluidic instability and the induced flow instability conditions can enhance the mixing efficiency.