Acoustic micromixing in a serpentine channel with sharp teeth for controllable nanomaterial synthesis

Acoustic micromixers have attracted considerable attention due to their rapid and efficient mixing capabilities, along with their flexibility, non-invasive operation, and strong compatibility, making them highly promising for applications in chemical analysis, drug development, and nanomaterial synthesis. However, the inherent limitation of low throughput and lack of stability restricts their broader application. In this study, we present an acoustic micromixer integrating both acoustic and inertial effects to generate multiple micro-vortices inducing three-dimensional convection for enhanced nanomaterial production. The device consisted of a serpentine channel with staggered sharp teethes on both sidewalls and a piezoelectric transducer (PZT) placed on top of the channels. The parameters such as PZT position, polydimethylsiloxane (PDMS)/glass thickness, sharp teeth density, and acoustic intensity influencing the mixing efficiency were firstly explored. Then the micromixer was validated to enable rapid and efficient mixing across a Reynolds number (Re) range of up to 323.46 (with flow rates reaching 3500 μL/min) at a steady low-frequency (0.4 kHz) acoustic wave, with a low power consumption of only 1.9 mW. The Re range is doubled compared to those reported in similar studies. Additionally, visualization of flowing beads and numerical simulations have revealed the flow patterns and clarified the mixing mechanism, further confirming its capability for rapid and effective mixing. Furthermore, the micromixer was successfully utilized to synthesize size-tunable, monodisperse zeolitic imidazolate framework-8 (ZIF-8) nanoparticles and Ti₃C₂T_X/Pt-Pd nanocomposites loaded with ultrasmall Pt-Pd bimetallic nanoparticles, highlighting its practicality and versatility for various applications.