Microfluidic Engineering of Microgels: A Review of Emerging Technologies, Materials, Fabrication Strategies, and Applications.

Microparticles of hydrogels, also known as microgels, have garnered extensive attention due to their versatile properties and wide range of applications in different fields of science, technology, and medicine. Among the developed technologies to produce microgels, the precise control over fluid handling offered by microfluidics enables particular fine-tuning of the shape, size, and composition of microgels. This article provides a review of recent progress in the development of microfluidic technologies for the fabrication of microgels based on different hydrogel-based biomaterials for diverse practical applications. The fundamental principles of different microfluidic-based techniques for microgel formation are summarized including chip-based, capillary-based, valve-based, three-dimensional printed, and digital microfluidics. Following, strategies for producing microgels from various natural and synthetic polymers using a range of potential crosslinking techniques with varying sizes, structures (water-in-oil, oil-in-water, higher order emulsion, and core-shell), and morphologies (spherical, non-spherical, Janus, and porous) are discussed in detail. Subsequently, the practical applications of microgels produced via microfluidic technologies are summarized across various fields including cell encapsulation, tissue engineering, particle removal, sensors, and food and nutrition, with current challenges and opportunities highlighted to motivate future research in the field.