Tough PEG-only hydrogels with complex 3D structure enabled by digital light processing of "all-PEG" resins

Digital light processing (DLP) of structurally complex poly(ethylene glycol) (PEG) hydrogels with high mechanical toughness represents a long-standing challenge in the field of 3D printing. Here, we report a 3D printing approach for the high-resolution manufacturing of structurally complex and mechanically strong PEG hydrogels via heat-assisted DLP. Instead of using aqueous solutions of photo-crosslinkable monomers, PEG macromonomer melts were first printed in the absence of water, resulting in bulk PEG networks. Then, post-printing swelling of the printed networks was achieved in water, producing high-fidelity 3D hydrogels with complex structures. By employing a dual-macromonomer resin containing a PEG-based four-arm macrophotoinitiator, "all-PEG" hydrogel constructs were produced with compressive toughness up to 1.3 MJ m(-3). By this approach, porous 3D hydrogel scaffolds with trabecular-like architecture were fabricated, and the scaffold surface supported cell attachment and the formation of a monolayer mimicking bone-lining cells. This study highlights the promises of heat-assisted DLP of PEG photopolymers for hydrogel fabrication, which may accelerate the development of 3D tissue-like constructs for regenerative medicine.