Fluid Mixing Control Inside a Y-shaped Microchannel by Using Electrokinetic Instability

Abstract

A parametric study was conducted to improve our understanding pertaining to the fundamental physics of electrokinetic instability (EKI) and to explore the effectiveness of manipulating EKI waves to control/enhance fluid mixing inside a Y-shaped microchannel. The dependence of the critical strength of the applied static electric field to trigger the EKI waves on the conductivity ratio of the two mixing streams inside the Y-shaped microchannel was quantified at first. The effects of the applied electric field strength on the evolution of the EKI waves and the resultant fluid mixing were assessed in terms of scalar concentration distributions, shedding frequency of the EKI waves and fluid mixing efficiency. The effectiveness of manipulating the EKI waves by adding alternative perturbations to the applied static electric fields were also explored for the further enhancement of the fluid mixing inside the Y-shaped microchannel. The measurement results revealed that the relationship between the critical strength of the applied static electric field and the conductivity ratio of the two mixing streams in the Y-shaped microchannel can be represented well by a power function with the power index about -0.246. The fluid mixing efficiency was found to increase monotonically with the increasing strength of the applied electric field. The fluid mixing process was found to be further enhanced by adding alternative perturbations to the applied static electric fields with the mixing process being most enhanced when the frequency of the alternative perturbation is close to the natural shedding frequency of the EKI waves. The fluid mixing efficiency was found to increase rapidly as the amplitude of the alternative perturbation increases.