Cavitation behavior and mixing performance of antisolvent precipitation process in an ultrasonic micromixer

A facile and robust ultrasonic micromixer was developed to intensify antisolvent precipitation via ultrasonic cavitation. The gas supersaturation created from solvent–antisolvent mixing was found to be a novel driving force which facilitated the generation of cavitation bubbles (CBs). Instead of being attached on the channel wall, numerous CBs translated across the microchannel at a speed up to 1.7 m/s, inducing intense transverse flow over the cross-section. The unique cavitation behavior enabled rapid mixing (mixing time 15–45 ms at 30 W) of solvent–antisolvent over wide Reynolds number range (70–500) and flow rate ratio (5:1–2:3), providing better operability for antisolvent precipitation. The effects of ultrasonic power, total flow rate, flow rate ratio, and solvent on cavitation behavior and mixing performance were quantitatively studied. Finally, the potential of the ultrasonic micromixer as a new tool for antisolvent precipitation was demonstrated by synthesizing size-controllable and monodisperse polymeric nanoparticles in a high-throughput and reproducible manner.