Structurally Trapped Microbubble-Induced Acoustic Mixing in 3D-Printed Microchannels

We conduct experimental investigations into mixing promoted by bubble-induced acoustic streaming in a 3D-printed resin chip. Resin-printed comb-like structures on the lateral microchannel wall are used to trap microbubbles, which upon acoustic excitation generate microvortices in the fluid confined in the microchannel. Stereolithography (SLA) printing not only offers the ease of printing such intricate features but also ensures rapid fabrication of the chip. We demonstrate how the bubble-induced microvortices, spanning transverse to the direction of flow, can promote enhanced dye mixing. We show how manipulation of operating conditions like frequency and applied voltage and modulation of the geometrical features offer ease of control over the mixing process. Based on the results presented in this study, we conclude that such acoustofluidic devices working on the principles of bubble-induced acoustic streaming hold potential for significant mixing intensification in low Reynolds number settings.