Versatile molecular slide-rings for the construction of composite hydrogel sensors

Hydrogel matrices for flexible electronic devices need to meet multiple criteria, including robust mechanical properties, appropriate skin adhesion, and high conductivity. Conventional hydrogels, however, often suffer from limitations such as hysteresis fatigue, poor adaptability, and structural fragility. In this work, we designed a series of polymerizable, water-soluble molecular slide-ring (MSR) units with precise host-guest molar ratios. These MSRs are based on bile acid guests functionalized with hydrophilic poly(ethylene glycol) chains of varying lengths, which specifically recognize host acrylate β-cyclodextrins. Subsequent photopolymerization of the MSRs with acrylamide yielded a range of SR hydrogels exhibiting wide tensile fracture strains and low hysteresis. Furthermore, the incorporation of nanoclay particles of laponite-RDS led to a composite slide-ring hydrogel system with improved toughness, high strength, and stable sensing performance. The composite hydrogel-based sensors not only demonstrate excellent skin adhesion and minimal skin irritation, but also monitor human motion and electrocardiogram signals with high sensitivity in both humans and mice, highlighting their potential for flexible wearable electronics. This study addresses key synthetic challenges associated with traditional slide-ring hydrogels and establishes a new paradigm for developing high-performance slide-ring materials using versatile MSRs.