Initiator-Free Supramolecular Zwitterionic Gels for Skin-Inspired Soft Iontronics

Conventional synthetic skin for intelligent soft robotics typically relies on thermally or UV-initiated polymerization, making initiator-free rapid gelation a persistent challenge. Here, a supramolecular Lewis acid-base gelation strategy that enables facile, initiator- and crosslinker-free synthesis of polyzwitterionic gels is presented. Strong hydrogen bonding between urea (hydrogen bond donor, HBD) and the zwitterionic moieties of 2-methacryloyloxyethyl phosphorylcholine (MPC; polymerizable zwitterionic hydrogen bond acceptor, PZHBA) drives spontaneous polymerization, establishing a general platform for zwitterionic gelation in deep eutectic solvents (DESs), such as choline chloride (ChCl) and urea. Inspired by the structural and ionic complexity of human skin, zwitterionic supramolecular eutectogel (ZSE) is designed via copolymerization of N-acryloyl glycinamide (NAGA) and MPC in DES, yielding a bioinspired ion-hydrogen bond dynamic network. These gels exhibit tunable mechanical properties, including an ultralow Young's modulus (5-180 kPa), and exceptionally high ionic conductivity (2 S·m^-1), which arises from the solvation of zwitterionic groups. The dynamic supramolecular network also imparts recyclability and intrinsic self-adhesion. ZSEs can be continuously spun into highly sensitive strain sensors with environmental robustness for integration into textiles. Additionally, bio-optimized gel patches demonstrate excellent antibacterial activity and biocompatibility. This work offers a sustainable and versatile synthetic platform for next-generation soft iontronics and bioinspired human-machine interfaces.