Fabrication of Microgel-Reinforced Hydrogels via Vat Photopolymerization

We report a facile method for the vat photopolymerization (i.e., digital light processing, DLP) of microgel-reinforced hydrogels that leverages both light and dark polymerization for curing. As an example, norbornene modified hyaluronic acid (NorHA) microgels at varying volume fractions swollen in acrylamide monomer are implemented as resins. When processed with DLP, acrylamide polymerization and cross-linking results in the formation of a secondary, continuous network that percolates through the microgels. At even low volume fractions (e.g., 30% v/v), the addition of microgels results in up to 4-fold increases in the stress at failure and work of fracture and a reduction in hydrogel swelling. The microgel-reinforced hydrogels are 3D printed into intricate shapes (e.g., metamaterial lattices) while maintaining uniform microgel distributions, and microgels with varied cross-link densities, cross-linkers, and fabrication methods are also investigated. This work expands the potential of microgel-reinforced hydrogels across applications where geometric freedom is essential.