Microfluidic mixing with electrokinetic instability stirring by electrical field intensity perturbations

This paper investigates the electrokinetic instability (EKI) phenomenon in a T-type microchannel, in which two aqueous electrolyte solutions with a 10:1 conductivity ratio are driven electrokinetically into the mixing channel via the application of a DC electrical field. It is found that fluctuating, unstable waveforms are formed in the entrance region of the mixing channel and then propagate in the downstream direction when the intensity of the electrical field is increased beyond a certain critical threshold value. Electrical field intensity perturbations aligned in the direction of the conductivity gradient are then added to the DC electrical field at the upper inlet of the T-type microchannel. It is found that the application of the electrical field intensity perturbations induces flow instability conditions, and hence improves the mixing efficiency. Furthermore, these perturbations stir the microfluidic instability and can reduce the required critical threshold value of the applied DC electric field intensity.