3D Printable Active Hydrogels with Supramolecular Additive-Driven Adaptiveness

Smart hydrogels are a promising candidate for the development of next-generation soft materials due to their stimuli-responsiveness, deformability, and biocompatibility. However, it remains challenging to enable hydrogels to actively adapt to various environmental conditions like living organisms. In this work, supramolecular additives are introduced to the hydrogel matrix to confer environmental adaptiveness. Specifically, their microstructures, swelling behaviors, mechanical properties, and transparency can adapt to external environmental conditions. Moreover, the presence of hydrogen bonding provides the hydrogel with applicable rheological properties for 3D extrusion printing, thus allowing for the facile preparation of thickness-dependent camouflage and multistimuli responsive complex. The environmentally adaptive hydrogel developed in this study offers new approaches for manipulating supramolecular interactions and broadens the capability of smart hydrogels in information security and multifunctional integrated actuation. In this work, 2-ureido-4-pyrimidinone (UPy) supramolecular additives are integrated into the poly(N-isopropylacrylamide-co-acrylamide) (PNIPAM-co-AAm) matrix to create environmentally adaptive poly(N-isopropylacrylamide-co-acrylamide)-UPy (PNAU) hydrogels. The adaptive microstructures, swelling properties, mechanical performance, and transparency can be controlled by UPy additives and their aggregation in the deswelling process. Additionally, the outstanding 3D printability of PNAU hydrogels broadens their applications in multifunctional counterfeiting and actuators. image