Mixing intensification in an acoustofluidic micromixer aided with micro-pillars

Abstract

In this work, we present an acoustofluidic micromixer that employs the combination of acoustic waves and micro-pillars to achieve enhanced mixing performance. We have shown that micro-pillars can generate micro-vortices, which lead to intense stretching and folding of the fluid trapped inside the micromixer and subsequently result in the formation of lamellar structures consisting of layers of the stretched fluids having steep concentration gradients between them. High concentration gradients coupled with the increased interfacial area result in higher rates of molecular diffusion. A numerical study is conducted, testing the performance of micro-pillars of three different designs in comparison to a simple rectangular acoustofluidic micromixer without any micro-pillars. The performance of the device in terms of improving the reaction kinetics of a chemical process has also been analyzed. For wide aspect ratio microchannels, our acoustofluidic micromixer helps in achieving rapid and homogeneous mixing while maintaining a high throughput.