4D printed polymethacrylate lattices capable of dimensional switching and payload release via photoresponsive actuation of azobenzene units

In this report, we demonstrate the synthesis of photoresponsive polymeric hydrogel lattices using stereolithographic 3D printing to afford objects that can change shape when irradiated with UV-vis light. Methacrylate-based monomers featuring azobenzene units were used as the photo-actuator components. Co-polymerisation of these monomers with 2-hydroxyethyl methacrylate produced well-defined hydrogel lattices. Photo-actuation of the hydrogels led to contraction of the 3D printed lattices up to 23% by volume. The ability of such photoresponsive hydrogel lattices to exhibit payload release has been studied using methylene blue as a drug mimic. Upon irradiation, the hydrogel lattice was squeezed like a sponge through photo-induced actuation in pulses, resulting in the controlled release of the pro-drug over 24 hours.