Highly stretchable and anti-freezing gelatin-based ionic conductive hydrogels regulated by ionic liquid and metal...

Flexible ionic conductive hydrogels that simultaneously combine large stretchability, anti-freezing capability, and stable electrical conductivity are highly desirable for wearable sensing and self-powered energy devices, yet their integrated design remains challenging. Herein, an ionic conductive hydrogel was developed through a multicomponent regulation strategy by coupling a semi-interpenetrating gelatin/poly(acrylamide-co-acrylic acid) (Gel/P(AM-co-AA)) network with ionic liquids 1-butyl-3-methylimidazolium chloride ([BMIm]Cl) and Zr⁴⁺-induced metal coordination interactions. The multiple dynamic interactions within the hydrogel network endowed the hydrogel with balanced stretchability, mechanical strength, ionic conductivity, and low-temperature adaptability. The optimized hydrogel exhibited an elongation at break of 1079% and an ionic conductivity of 11.27 mS/cm at room temperature, while maintaining a conductivity of 8.66 mS/cm at -20 °C, demonstrating its anti-freezing conductive stability. Owing to these integrated properties, the hydrogel functioned as both a flexible strain-sensing material and a hydrogel electrode for a triboelectric nanogenerator (TENG). The hydrogel strain sensor showed a wide working range of 0-900% and a high gauge factor of 3.14, enabling human motion monitoring and Morse-code-based information output. In addition, the hydrogel-based single electrode TENG delivered an open-circuit voltage (Voc) of about 386 V and a maximum power density of 2483.08 mW/m², demonstrating its good energy-harvesting capability. The device also maintained stable electrical output at -20 °C, indicating its low-temperature applicability. Furthermore, the self-powered sensing function of the TENG was extended to handwriting recognition by combining it with a deep learning model, achieving an accuracy of 98.65%. This work provides an effective strategy for constructing highly stretchable and anti-freezing ionic conductive hydrogels for wearable sensing, self-powered electronics, and intelligent human-machine interaction (HMI).