Ultrasound-responsive microparticles from droplet microfluidics

Ultrasound (US)-responsive microparticles show broad potential in controlled drug delivery systems. Compare with the traditional micron-scale material fabrication methods, capillary microfluidic technology features superior advantages in large-scale production, batch-to-batch similarity, high encapsulation efficiency, low cost, and so on. The excellent maneuverability and customizability of the capillary microfluidic devices allow the production of microparticles with various functionalities and fine-tuned chemical compartments. Moreover, the flexible regulation of the particle size and core-shell ratio can be easily realized by modulating the capillary orifices and flow rates of microfluidic channels. In this review, we introduce the fabrication of US-responsive microparticles with specific core-shell structures via capillary microfluidic methods, from single emulsion to triple emulsions. Then, we address some particular examples, where the drug delivery and US-triggered cargo release capacity of these microfluidic microparticles are demonstrated. Finally, we conclude the advanced achievements of the US-responsive microfluidic microparticles, summarize the obstacles to the development of this interdisciplinary field, and prospect their future applications.