Self-Degradation of Digital Light 3D Printed Covalent Cross-Linked Hydrogel at Ambient Temperature

Photocuring-based three-dimensional (3D) printed hydrogels have versatile applications in various fields. However, the heterogeneous network with nanogel cross-linking points during free radical polymerization (FRP) often results in hydrogels that are unable to degrade or be reprocessed, significantly limiting their applications. Herein, a UV-curable reversible addition–fragmentation chain transfer (RAFT)-mediated hydrogel system compatible with digital light processing (DLP) 3D printing is reported, enabling the fabrication of complex hydrogel structures with rapid, controlled degradation and self-degradation capabilities at ambient temperature. The enhanced degradability stems from the synergistic combination of the hydrolyzable bonds and RAFT chemistry. The hydrogel precursors exhibit optimal rheological properties, while the mechanical properties of the resulting hydrogels are precisely tunable by adjusting the cross-linker content and water content. Degradation kinetics can be systematically controlled by adjusting the cross-linker content, water content, and the treatment temperature. Hydrogels containing 50 wt % water content demonstrate complete degradation into molecular chain segments and/or molecules within 6 h at 37 °C. Furthermore, the 3D printed RAFT-mediated hydrogels can self-degrade at ambient temperature. After self-degradation, the resulting solution exhibits the unsaturated acrylic functional molecules with the characteristic of high viscosity, which can be directly used for UV-assisted direct ink writing (DIW) to refabricate new 3D hydrogel structures.