Acoustic bubble-based bidirectional micropump

Efficient transportation of fluids and microparticles is an important capability in many medical and biological applications. In this article, an efficient bi-directional micropump using microcavity-trapped acoustic bubbles is studied. With acoustic actuation, a controllable microstreaming net flow is generated inside a microchannel by the oscillating bubbles. Based on theory and experimental results, different sized microbubbles have different resonant frequencies. Thus, by oppositely placing the different sized microbubbles, the flow direction can be switched via altering the frequency. The pumping flow rate can be tuned by adjusting the input voltage and can achieve as high as 1600 nl/min with high stability. Furthermore, the bi-directional pumping ability is also proved using blood-mimicking fluid (BMF), allowing for on-chip high-viscosity fluid pumping. In the end, the proposed device is employed in pumping Escherichia coli bacteria, indicating that the micropump is capable of pumping cells without damaging them. This inexpensive, portable and biocompatible acoustic bubble-based bi-directional pump for transporting fluids and particles has great potential to integrate with other on-chip platforms for multiple biological and chemical applications, such as drug delivery, cell separation, and chemical analysis.