Physically Cross-Linked Biopolymer-Based Strong and Stretchable Organohydrogel with Self-Healing and Biocompatibility for Environmentally Tolerant Strain Sensors

The development of wearable strain sensors increasingly focuses on multifunctional materials that integrate mechanical robustness, self-repairing capacity, temperature-resilient conductivity, and biocompatibility. Herein, we developed a physically cross-linked biopolymer-based organohydrogel by incorporating gelatin (Gel) and β-cyclodextrin-grafted chitosan (CDCS), designated as Gel/CDCS, reinforced through hydrogen bonding, ionic interactions, and host-guest complexation. The optimized Gel/CDCS1 organohydrogel with 1% of CDCS exhibited outstanding stretchability, with a tensile strain at break of 410.9% and a tensile strength of 92.2 kPa, while maintaining 85% of its mechanical properties after self-healing at 40 °C. The introduction of kosmotropic salts (Na₃Cit and NaCl) and a glycerol-water binary solvent system conferred remarkable environmental adaptability, allowing stable performance from -20 to 37 °C. Notably, it achieved a high ionic conductivity of 0.946 S m^-1 at room temperature, alongside 0.606 S m^-1 at -20 °C and 0.330 S m^-1 at 37 °C, ensuring operation under extreme conditions. The strain sensor displayed high sensitivity with a gauge factor (GF) increasing from 1.06 to 1.34 over a broad strain range and maintained a stable electrical response over 600 consecutive stretching cycles. Additionally, it enabled reliable detection of diverse human motions, including facial expressions, joint bending, and breathing, demonstrating excellent conformability and signal stability during on-body monitoring. Additionally, Gel/CDCS1 exhibited excellent biodegradability, degrading by over 80% in soil within 4 days, and showed high biocompatibility with fibroblast viability of around 80%. These attributes establish Gel/CDCS1 as a promising eco-friendly candidate for next-generation flexible electronics, wearable strain sensors, and biomedical applications.