Stretchable, Self‐Healing, and Bioactive Hydrogel with High‐Functionality N,N′‐bis(acryloyl)cystamine Dynamically Bonded Ag@polydopamine Crosslinkers for Wearable Sensors

Abstract Hydrogels present attractive opportunities as flexible sensors due to their soft nature and tunable physicochemical properties. Despite significant advances, practical application of hydrogel‐based sensor is limited by the lack of general routes to fabricate materials with combination of mechanical, conductive, and biological properties. Here, a multi‐functional hydrogel sensor is reported by in situ polymerizing of acrylamide (AM) with N,N′‐bis(acryloyl)cystamine (BA) dynamic crosslinked silver‐modified polydopamine (PDA) nanoparticles, namely PAM/BA‐Ag@PDA. Compared with traditional polyacrylamide (PAM) hydrogel, the BA‐Ag@PDA nanoparticles provide both high‐functionality crosslinks and multiple interactions within PAM networks, thereby endowing the optimized PAM/BA‐Ag@PDA hydrogel with significantly enhanced tensile/compressive strength (349.80 kPa at 383.57% tensile strain, 263.08 kPa at 90% compressive strain), lower hysteresis (5.2%), improved conductivity (2.51 S m−1) and excellent near‐infrared (NIR) light‐triggered self‐healing ability. As a strain sensor, the PAM/BA‐Ag@PDA hydrogel shows a good sensitivity (gauge factor of 1.86), rapid response time (138 ms), and high stability. Owing to abundant reactive groups in PDA, the PAM/BA‐Ag@PDA hydrogel exhibits inherent tissue adhesiveness and antioxidant, along with a synergistic antibacterial effect by PDA and Ag. Toward practical applications, the PAM/BA‐Ag@PDA hydrogel can conformally adhere to skin and monitor subtle activities and large‐scale movements with excellent reliability, demonstrating its promising applications as wearable sensors for healthcare.