Microfluidic micromixing by micropost-based acoustic microstreaming

Abstract

1. INTRODUCTION

Microfluidic mixing is important in many applications, including biology, chemistry, and drug delivery. In active methods, external forcing creates additional mixing interfaces to enhance molecular exchange. Passive techniques utilize features of the channel geometry to increase mixing. Acoustic microstreaming-based microfluidic mixing is promising but has so far been limited due to high costs and low mixing efficiency[1]. We aim to introduce a novel acoustic mixing concept, which can be very useful for micromixing applications with channels of high aspect ratios (i.e., very wide channels) where other acoustic techniques (wall-based actuators) are much less effective.

2. Materials and methods

We employ acoustics to disturb and thereby mix fluids in a microfluidic device. The microfluidic device is fabricated by soft lithography, and a transducer is attached to the glass substrate of the device to enable acoustic excitation [2]. We create micropillars inside the microchannel using stop-flow lithography. The transducer actuation leads to the vibration of the glass substrate, which in turn, vibrates the posts inside the microfluidic channel such that microstreaming flows are generated around each pillar. The microstreaming flow significantly enhances the fluid mixing inside the channel [3].

3. Results

We have created a robust protocol to examine mixing performance quantitively by designing a setup to avoid flow fluctuations over time and monitor mixing using an inverted microscope. We investigate different parameters in the micropillar-fabrication slit channel lithography process to create various shapes and stiffness microposts. Finally, we also evaluate the resulting mixing performance from these parameter changes.

4. Conclusion

We aim to perform parameter sweeps for transducer power, micropost geometry and stiffness, and microchannel geometry to optimize the microfluidic acoustic micromixing platform. Achieving the goal of optimizing mixing performance will lead to benefits in applications in biology, chemistry, and other fields. 

REFERENCES

[1] Li, Z., et al., A review of microfluidic-based mixing methods. Sensors and Actuators A: Physical, 2022: p. 113757.

[2] Salari, A., et al., Dancing with the Cells: Acoustic Microflows Generated by Oscillating Cells. Small, 2020. 16(9): p. 1903788.

[3] Zhao, S., et al., Fabrication of tunable, high-molecular-weight polymeric nanoparticles via ultrafast acoustofluidic micromixing. Lab on a Chip, 2021. 21(12): p. 2453-2463.