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research-article

Time-periodic electroosmotic flow with non-uniform surface charges

[+] Author and Article Information
Hyunsung Kim

School of Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164-2920
hyunsung.kim@wsu.edu

Aminul Khan

School of Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164-2920
aminulislam.khan@wsu.edu

Dr. Prashanta Dutta

School of Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164-2920
prashanta@wsu.edu

1Corresponding author.

ASME doi:10.1115/1.4042469 History: Received September 05, 2018; Revised January 02, 2019

Abstract

Mixing in a microfluidic device is a major challenge due to creeping flow, which is a significant roadblock for development of lab-on-a-chip device. In this study, an analytical model is presented to study the fluid flow behavior in a microfluidic mixer using time-periodic electroosmotic flow. To facilitate mixing through micro-vortices, non-uniform surface charge condition is considered. A generalized analytical solution is obtained for the time-periodic electroosmotic flow using a stream function technique. The electroosmotic body force term is accounted as a slip boundary condition on the channel wall, which is a function of time and space. To demonstrate the applicability of the analytical model, two different surface conditions are considered: sinusoidal and step change in zeta potential along the channel surface. Depending on the zeta potential distribution, we obtained diverse flow patterns and vortices. The flow circulation and its structures depend on channel size, charge distribution, and the applied electric field frequency. Our results indicate that sinusoidal zeta potential distribution provides more effective mixing potential than step change in the zeta potential. This analytical model is expected to aid in the effective micromixer design.

Copyright (c) 2019 by ASME
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