Stretchable freezing-tolerant triboelectric nanogenerator and strain sensor based on transparent, long-term stable, and highly conductive gelatin-based organohydrogel

Conductive hydrogels have attracted tremendous attention for the next-generation electronic/energy/robotic application owing to their excellent mechanical and electrical properties, including stretchability, high conductivity, and stability. How to simultaneously realize their highly transparent, self-healing, antifreezing/antidrying, biocompatible and highly conductive features through a simple approach is still a challenge. Herein, the stretchable freezing-tolerant triboelectric nanogenerator (TENG) and strain sensor have been developed based on a transparent, long-term stable, and highly conductive gelatin/NaCl organohydrogel (GNOH), which is prepared via a facile immersion strategy in a glycerol/water binary solvent. The GNOH demonstrates superior merits of strain (300%), transparency (85%), high conductivity (1.6 S/m), freezing tolerance (−20 ℃), self-healing capability (91%), and environment stability (over 30 days). Furthermore, the wearable strain sensors enable the detecting, quantifying, and monitoring of human activities with high sensitivity of about 2.5 (strain of 0–200%). Meanwhile, the fabricated TENG in single-electrode mode can achieve excellent electrical outputs to power portable electronics when efficiently harvesting biomechanical energies, even at harsh cold temperature (−20 ℃). Additionally, a flexible self-powered calculator based on the arrayed TENG as touch panel is also explored for human-machine interaction (HMI). This study paves the way for potential applications in wearable electronics, healthcare monitoring, biomechanical energy harvesting and HMI.