Comprehensive experimental and numerical investigation of a microrod-based active micromixer driven by the magnetic stirring mechanism

Abstract

Background

The mixing process at the microscale is a complex challenge in microfluidic science, where implementing micromixers can facilitate effective mixing on lab-on-a-chip systems. Despite the advances, low mixing index, long mixing channel length, and lack of mixing controllability are still challenging in micromixers.

Methods

The mixing efficiency of two distinct micromixers with different mixing zones, where a microrod is actuated by a magnetic field generated by a laboratory magnetic stirrer, was investigated numerically and experimentally. In addition, a square-shaped splitting and recombination channel was introduced into the micromixer's geometry to incorporate the advantages of both passive and active strategies.

Significant findings

The efficiency of mixing processes is significantly improved with an increased swing range of the oscillatory microrod. By changing the oscillation frequency of the microrod from 0 to 21 Hz, the mixing index increased from 70 % to 99 %. In contrast, the increasing fluid flow rate from 100 to 1000 μl/min has an inverse effect on the mixing index because of reducing residence time. Also, the viscosity of fluid has an inverse relationship with the mixing index. Finally, a predictive equation for the mixing index as a function of the affecting parameters was proposed using curve fitting and a genetic algorithm.