Oxygen-Inhibition Driven Compartmentalization of Dextran Microgels: Toward Fusible Colloidal Biomaterial Inks for 3D Printing.

This study presents a facile and versatile method to synthesize tailored, compartmentalized, polysaccharide-based microgels, with ultra-low crosslinked shells for the development of self-setting colloidal biomaterial inks. Compartmentalization is achieved by exploiting spatially controlled oxygen-inhibition of the crosslinking process in droplets obtained by droplet-based microfluidics, leading to physically distinct core and shell regions inside dextran microgels. The shell exhibits a markedly lower cross-linking density, resulting in reduced stiffness, tunable degradation, and higher macromolecular permeability than the core. The facile control of the core-to-shell ratio by varying the initiator concentration and oxygen availability represents a novel strategy to engineer microgel compartmentalization. This work establishes oxygen-controlled photopolymerization as a new design principle for structuring microgels in flow, offering precise spatial control over polymer network architecture without complex templating or multi-phase emulsions. Beyond dextran, this concept is broadly applicable to other acrylated and methacrylated hydrogel systems, opening new avenues for designing hierarchical soft materials. We demonstrate the applicability of these advanced microgels for the fabrication of millimeter-sized tissue constructs, via 3D printing by exploiting the fusion of ultra-low crosslinked shell compartments, thereby eliminating the need for additional chemical crosslinkers, initiators, or support baths to stabilize the final printed constructs.