Figure 1.

Overview of granular hydrogels. A) Defining characteristics of granular materials. These contrast other particulate matter, such as colloids (size < 10 μm; thermal forces > gravitational forces), foams (particles of air), and emulsions (particles of water). B) Particle jamming occurs when particles are packed above a minimum particle-volume fraction (and under suitable conditions of stress and temperature). Particles configured here are closer to random close packing with a particle-volume fraction of 0.64. The network of contact forces between neighboring particles is indicated by black lines. C) Inherent and tunable properties of granular hydrogel scaffolds. Microporosity: Micron-sized particles result in micron-sized pores that are similar to cell size. Interlinking: Particles can be interlinked in a variety of ways to form a stable structure. Heterogeneity: Granular scaffolds can incorporate a heterogeneous mix of particle species, such as porous particles, layered particles, particles encapsulating cells or small molecules, or particles of varying shapes.