Microgel technology has emerged as a powerful and versatile tool for regenerative medicine and tissue engineering applications. Just like their bulk counterparts, microgels are characterized by high water content, tunable physicochemical properties, and mimicry of the native extracellular environment. Owing to the advances in fabrication techniques, microgels can be produced in different shapes and sizes from a range of natural and synthetic polymers. They can also be utilized for controlled encapsulation of cells and therapeutics. One of the main advantages of microgels in comparison to traditional bulk hydrogels is that they are readily injectable thus allowing minimally invasive delivery of cellular cargo, drugs, or biological scaffolding for tissue repair. Furthermore, modular microgel systems are easily attainable by mixing microgel populations with distinct properties, while embedding microgels in conventional hydrogels provides a route towards soft matter composites. When many microgels are packed into a jammed state, they give rise to granular gels, bulk materials with dynamic macroscale properties governed by complex interactions of its constituents at the microscale. Solid-like at rest, granular gels reversibly transition into a liquid-like state when subjected to sufficient stress. This shear-thinning and self-healing property makes granular gels ideal material systems for tissue repair and 3D printing applications.

The aim of this Methods Collection is to present methods including, but not limited to microgel fabrication, microgel-based bio-ink formulation, injectable granular gels, and granular gel supports for embedded 3D printing.