Novel Study on the Mixing Mechanism of Active Micromixers Based on Surface Acoustic Waves
Honglin Lv, Xueye Chen
Abstract
The method of using a surface acoustic wave (SAW) to drive fluid mixing on a microfluidic chip has been widely investigated by researchers because of its advantages of not directly contacting the fluid and not changing the chemical properties of the fluid. In this paper, we investigate the potential mechanism of SAW-driven fluid mixing. A SAW device is designed by us and modal and harmonic response analyses are performed on it. Because the mechanisms of the traveling SAW (TSAW) and the standing SAW (SSAW) on a fluid are different, we have performed transient simulations for each of them in order to clearly understand their differences. The effect of voltage values on the intensity of acoustic pressure is also studied by us. Finally, we perform a comprehensive analysis of acoustic-fluid force-driven fluid mixing. For TSAW- and SSAW-driven fluid mixing, we discuss and analyze the mixing effect at different voltages separately. The velocity fields of the two types of SAW-driven micromixers are also investigated. It is found that the mixing effect of both micromixers is enhanced with increasing voltage. However, the TSAW-driven micromixer produces a single vortex flow through the channel in the acoustic action region, while the SSAW-driven micromixer produces a symmetric double vortex flow. The difference between the TSAW- and SSAW-driven fluids can be clearly analyzed by the velocity field results. The TSAW drives the fluid mainly on one side of the microchannel, while the SSAW drives the fluid by superposition of the acoustic flow force on both sides of the microchannel. The results of this study contribute to a better understanding of the SAW-driven effect on the flow properties of fluids. Moreover, this work lays a theoretical foundation for practical applications in areas such as biochemical reactions and polymer synthesis.