4D-Printable Photocrosslinkable Polyurethane-Based Inks for Tissue Scaffold and Actuator Applications

4D printing recently emerges as an exciting evolution of conventional 3D printing, where a printed construct can quickly transform in response to a specific stimulus to switch between a temporary variable state and an original state. In this work, a photocrosslinkable polyethylene-glycol polyurethane ink is synthesized for light-assisted 4D printing of smart materials. The molecular weight distribution of the ink monomers is tunable by adjusting the copolymerization reaction time. Digital light processing (DLP) technique is used to program a differential swelling response in the printed constructs after humidity variation. Bioactive microparticles are embedded into the ink and the improvement of biocompatibility of the printed constructs is demonstrated for tissue engineering applications. Cell studies reveal above 90% viability in 1 week and approximate to 50% biodegradability after 4 weeks. Self-folding capillary scaffolds, dynamic grippers, and film actuators are made and activated in a humid environment. The approach offers a versatile platform for the fabrication of complex constructs. The ink can be used in tissue engineering and actuator applications, making the ink a promising avenue for future research. Hosseinabadi and coworkers develop a generation of single material (non-composite) actuators by synthesis of photocrosslinkable polyurethanes. Reaction time is adjusted for tuning molecular weight distribution and properties of 4D/DLP printed constructs. Achieved cellular scaffolds exhibit 90% viability, and 50% biodegradation rate during 4 weeks of culture. Printed actuators can transport objects five times their weight by controlling atmospheric humidity.image