Ultrastretchable, Self-Adhesive, UV-Shielding Conductive Hydrogel as a Flexible Wearable Sensor for Human–Machine Interaction
Wen Liu, Mingjie Liu, Ying Li, YuanTao Liao, Yeying Lin, Chuyang Xiang, Yangengchen Zhong, Tianhua Xiao, Peng Yu, Chengyun Ning, Lei Zhou, Guoxin Tan
Abstract
Conductive hydrogels are promising candidates for next-generation wearable electronics due to their flexibility, biocompatibility, and ion-conductive properties. However, achieving a balance among electrical conductivity, mechanical robustness, interfacial adhesion, and environmental stability remains a key challenge. Herein, we present a multifunctional hydrogel synthesized via a one-pot free radical polymerization of acrylic acid, methacryloxyethyltrimethylammonium chloride, tannic acid, and calcium ions. The designed hydrogel exhibits ultrastretchability (strain up to 2900%) and strong interfacial adhesion (160.92 kPa) owing to a synergistic cross-linked network formed by hydrogen bonding, ionic complexation, coordination, and covalent interactions. Adhesion capacity remains above 80% after ten peel cycles, indicating persistent interfacial coupling. It exhibits two linear sensitivity regimes, with gauge factors of 1.9 below 300% strain and 2.5 up to 1000%, and maintains stable electrical performance over 300 cycles. Its high ionic conductivity (30.24 mS/cm) supports low-impedance signal transmission, while its intrinsic UV-shielding property, derived from the catechol chemistry of tannic acid, enables reliable outdoor operation. The hydrogel also exhibits a rapid response time of 65 ms, allowing accurate detection of dynamic biomechanical signals. This conductive hydrogel holds great promise for real-time monitoring of human motion and microexpressions, as well as for secure communication applications such as Morse code encryption. This hydrogel design offers a promising route toward next-generation wearable electronics with potential applications in smart healthcare, human-machine interaction, and secure communication.