Vat Polymerization 3D Printing of Hydrogels With Tunable Porosity.

Three-dimensional, interconnected hydrogel networks are central to tissue engineering and disease modeling, where tailored pore architecture and mechanical robustness are essential for supporting cellular functions. However, the limited ability to engineer microstructural features in vat polymerization 3D-printed natural hydrogels often compromises scaffold performance, as oversized pores reduce cell attachment and cell-cell interactions while smooth pore walls lack essential topographical cues. Here, we report an emulsion-based ink for vat polymerization 3D printing that enables the fabrication of hydrogels with finely tunable and highly interconnected porous architectures. An oil-in-water resin formulated using gelatin methacrylate (GelMA) contains stable solvent nanodroplets that act as sacrificial templates during photopolymerization. Removal of the dispersed phase yields additive-free porous hydrogels with pore sizes ranging from 0.66 to 46.15 µm and a 2.5-fold enhancement in compressive toughness. This strategy is compatible with digital light processing (DLP) and broadly applicable to multiple photocurable biopolymers, including alginate methacrylate (ALMA) and hyaluronic acid methacrylate (HAMA). The resulting porous scaffolds promote enhanced cell attachment, proliferation, and cell-cell interactions, highlighting the potential of this vat polymerization-compatible platform for advanced biofabrication.