Gelatin Enhanced Gels with Superior Self-Healing and Freezing-Tolerant Properties for Multifunctional Flexible Strain Sensors

Hydrogels with integrated attributes of mechanical toughness, transparency, self-healing ability, and freezing tolerance have attracted tremendous attention because of their promising applications in advanced intelligent systems, flexible energy storage devices, and wearable electronics. Herein, we developed a multifunctional gel polymer with hybrid double network structures by introducing the biological macromolecular chains of gelatin and chemically cross-linked DMA (N,N-dimethylacrylamide)-AA (acrylic acid) chains into the binary solvent of ethylene glycol and water. Due to the synergy of the double networks and abundant dynamic noncovalent interactions, the as-prepared gel exhibits high stretchability (up to 1070%), excellent tensile strength (up to 102 kPa), and good self-healing efficiency (up to 85%), which can serve as a sensitive, fast-responsive, and durable strain sensor with self-healing function for real-time detection of different parts of human movements (finger, wrist, elbow, neck, and keen). Noticeably, in view of the inhibitory effect of ethylene glycol molecules on ice crystal growth, a freezing-resistant communication device based on the gel sensor is successfully designed, which can encrypt and transmit various messages to the receiver even in an extremely cold environment of −35 °C. We believe that this work will provide a feasible method to construct mechanically toughened, self-healing, and low-temperature tolerant flexible materials for versatile applications in wearable electronics.