Trehalose-mediated anti-freezing and heat-resistant chitosan-based conductive hydrogels with tunicate cellulose nanocrystals for antibacterial wearable sensors.

Conductive hydrogels based on natural products are promising for wearable sensors owing to their low cost and good biocompatibility, but typically suffer from poor mechanical strength, limited environmental stability, insufficient antibacterial activity, single functionality, and poor electrical conductivity. Here, we develop a conductive nanocomposite hydrogel (CAT2T1.2L0.1) featuring trehalose as a natural cryoprotectant-a key design element of our system-along with tannic acid-coated tunicate cellulose nanocrystals (TA@TCNCs) as nano-reinforcements incorporated into a chitosan/acrylic acid network followed by LiCl immersion. The hydrogel integrates dynamic hydrogen bonds, lithium bonds, and Schiff base bonds, achieving high tensile strength (132.4 kPa) and ultrahigh elongation (3996.6%). Trehalose and LiCl synergistically suppress ice crystal formation and water evaporation, enabling stable flexibility and conductivity (4.81-5.0 S/m) from -30 °C to 60 °C. The hydrogel exhibits rapid self-healing (97.1% strain recovery within 12 h), broad-spectrum antibacterial activity (>94% kill rate), and excellent biocompatibility (cell viability 168.5%). As a wearable strain sensor, it enables wireless human motion monitoring and a deep learning-based handwriting recognition system with 93.4% accuracy, demonstrating great potential for extreme-environment flexible electronics.