Mechanical characterization of soft microparticles prepared by droplet microfluidics

Droplet microfluidics is one of the most promising approaches that allows preparation of microparticles with tailored structure and composition. Various functional microparticles have been developed using microfluidics, where their controlled structure shows high potential for a wide range of applications. Among these, soft polymeric microparticles which exhibit low elastic modulus compared to ceramics and metals are extensively investigated in biomedical applications due to their biocompatibility, high surface-to-volume ratio, as well as soft and deformable nature. As the mechanical properties of soft microparticles play important role in determining how they function in each application, it is essential to adequately characterize them for the optimal design of functional microparticles. In this review, we mainly discuss the mechanical characterization methods of soft microparticles and their elastic property. A brief overview of the droplet microfluidics-assisted fabrication of microparticles is also provided before discussing the mechanical characterization techniques. We then describe the general characterization methods and models employed to determine the elastic properties of microparticles. In addition, we discuss the relationship between the physical parameters (size, composition, and structure) and the elastic properties of the microparticles, followed by the role of elastic properties in various applications including microcarrier, bioink, and self-healing to name a few.