Micromixing via recirculatory flow generated by an oscillatory microplate

Abstract

Mixing in micro-environment has been explored in a number of studies. This study presents a unique approach of efficient mixing of two heterogeneous streams via two counter-rotating recirculatory streams induced by in-plane resonance of a rectangular microplate actuated via Lorentz force. The generated time-mean flow structure was interrogated for mixing efficacy over a range of excitation voltage, Reynolds number, and Pèclet number, along with numerical analysis to probe the time-mean flow physics. Results show that the recirculatory flow is generated at the plate's edges due to local flow non-linearity, characteristic of acoustic streaming. The percentage of mixing, at one device length-scale downstream, attains 93% at a low Reynolds number of 0.0037 (based on mean velocity of 0.078 mm/s and channel height of 50 lm) at 8 V excitation. Further characterization via enhanced diffusivity shows a maximum of 80.7-fold increase. Comparison with other active mixers shows the current device achieves mixing in one of the shortest distances. The proposed approach is robust, tunable to attain desired mixing characteristics and essentially independent of the properties of the fluid medium, which should be useful in a number of microfluidic applications requiring fast mixing.

The negative-differential-resistance (NDR) mechanism of a hydroelastic microfluidic oscillator

“…This suggests a broad applicability of the design for microfluidics. Potential applications include flow controls [11], mixing enhancement [25][26][27], cells separation [28] (McFaul et al) and analysis [29] (Roy et al) etc.…”

CFD study on laminar mixing at a very low Reynolds number by pitching and heaving a square cylinder

“…In comparison with Lu et al, this full mixing was thought to be due to the fluid going through the stirrer instead of passing around it as happened in [Lu et al, (2002)]. Lin et al presented a novel approach to achieve efficient mixing by using the Lorentz force to induce two counter-rotating streams producing a in-plane resonance of a rectangular microplate [Lin et al, (2011)]. After using different excitation voltages, Reynolds and Peclet numbers attained the maximum efficiency of around 93% at a Reynolds number of 0.0037 just one device length-scale downstream.…”