Zehui Shang,Yinan Liu,Chunying Zhu,Taotao Fu,Xiqun Gao,Youguang Ma
The breakup of water-in-water droplets in a Y-junction microchannel was experimentally investigated, focusing on the unobstructed breakup mode due to its broad applicability. This process was divided into four stages: entering, squeezing, pinch-off, and filament rupture, based on the evolution of the neck width and its thinning rate. In the entering stage, neck thinning accelerates with increasing dispersed-phase flow rate Q d , droplet length l 0 , and two-phase viscosity ratio λ , and slows down with increasing continuous phase flow rate Q c . In the squeezing stage, the minimum neck width follows a power-law relation with time. The thinning rate increases with higher Q d , l 0 , and λ , whereas increasing Q c inhibits thinning. In the pinch-off stage, neck width decreases linearly with time, and the thinning is enhanced by higher Q c , Q d , and l 0 , but remains nearly independent of λ . The filament rupture stage follows a power-law thinning trend, and exhibits similar parameter dependencies, though satellite droplets may form at high Q d and Q c , and show increased instability at low viscosity. These findings offer insights into neck dynamics and interfacial rupture in low interfacial tension systems.
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.
In this paper, we reported an effective microfluidic-based method for fast continuous synthesis of monodisperse PEG/SiO2 hybrid microspheres. The T-junction microfluidic chip equipped with rounded channels and the online photopolymerization system were applied for the microspheres microfabrication. The size of the microspheres was well controlled by the rounded channels and flow rate ratios of immiscrible fluids. We can obtain porous PEG microspheres when the hybrid microspheres were corroded by hydrofluoric acid. What's more, the interpenetrating polymer network structures of SiO2 microspheres were obtained after the hybrid microspheres treated via a calcination process.
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