Droplet Microfluidics for Producing Functional Microparticles

 Ju Hyeon Kim, Tae Yoon Jeon, Tae Min Choi, Tae Soup Shim, Shin-Hyun Kim, and Seung-Man Yang

[ABSTRACT] Isotropic microparticles prepared from a suspension that undergoes polymerization have long been used for a variety of
applications. Bulk emulsification procedures produce polydisperse emulsion droplets that are transformed into spherical microparticles through chemical or physical consolidation. Recent advances in droplet microfluidics have enabled the production of monodisperse emulsions
that yield highly uniform microparticles, albeit only on a drop-by-drop basis. In addition, microfluidic devices have provided a variety of means
for particle functionalization through shaping, compartmentalizing, and microstructuring. These functionalized particles have significant potential for practical applications as a new class of colloidal materials. This feature article describes the current state of the art in the
microfluidic-based synthesis of monodisperse functional microparticles. The three main sections of this feature article discuss the
formation of isotropic microparticles, engineered microparticles, and hybrid microparticles. The complexities of the shape,
compartment, and microstructure of these microparticles increase systematically from the isotropic to the hybrid types. Each
section discusses the key idea underlying the design of the particles, their functionalities, and their applications. Finally, we
outline the current limitations and future perspectives on microfluidic techniques used to produce microparticles