Microgels are 10-500 um hydrogel particles produced by microfluidic dropletting, emulsions or the application of shear during gelation. By changing fabrication parameters microgels can be tailored regarding their size, morphology, aspect ratio, particle stiffness and packing density. Altering these physical properties elucidates different local (cell-sensing) and global (as a bulk  matrix) mechanical properties. As a bulk, granular matrices act as yield stress materials with minimal thixotropy as adhesion forces between particles at rest overcome gravitational forces that would induce flow. When a critical stress is applied, they flow as structured fluids imparting injectability. Their bulk mechanics can be improved by introducing secondary crosslinking mechanisms activated post-injection.

Cooke et al., APL Bioengineering 2017

Fluid gels as a matrix to enable the injectable delivery of chondrocytes to the articular surface of the knee joint.

Dr. Cooke's work in bioprinting has overlap with this field as she uses microgels as the key component of suspension baths to overcome the limitations of low viscosity hydrogels materials. Read more about it here.