Alireza Mohammadzadeh - School of Mechanical Engineering, Sharif University of Technology
Mohammad Hassan Saidi - Sharif Energy Research Institute (SERI), Sharif University of Technology

Electrokinetic flow is a preferred framework for transport of fluids in microfluidic devices. They can be used as an active technique to improve mixing in various devices. Among all electrokinetic effects on fluid flow, the electrokinetic instability has been accepted as a promising fast kind of micromixer. One of the ways in which chaotic unstable flows can be established is when two fluids of great conductivity differences meet each other at the T-junction or Yjunction of a T/Y-microchannel for a specific range ofelectric field. The electric field when the first sustainable instability waves are formed in the channel is called the threshold electric field of instability. In this work first, we build a numerical model to predict electrokinetic instability in electro-osmotically drivenferrofluid/water co-flows through a T-shaped microchannel which could predict experimental trends of the previously reported study. Then the inlet channel angle is changed to form a Y-shaped channel from the T-shaped channel. Thus the effect of varying the inletchannel angle on the threshold electric field was investigated through the developed numerical model.The results demonstrated that the threshold electric field for the Y-shaped microchannel is significantly lower than that of the T-shaped channel no matter what is the inlet angle.

Electrokinetic Instability, Micromixer, Microfluidics, Electroosmotic flow