A multifunctional wearable hydrogel-based charge-trapping TENG enabling electrophysiological signal monitoring and high-efficiency energy harvesting with enhanced stability

Triboelectric nanogenerators (TENGs) offer a promising approach for harvesting high-entropy mechanical energy, while hydrogel-based sensors are ideal for wearable health monitoring due to their biocompatibility and stretchability. However, conventional charge injection techniques for enhancing TENG performance face challenges such as high voltage, limited durability, and incompatibility with hydrogel devices. To address these issues, we propose an electrowetting-assisted charge injection (EWCI) strategy integrated with an anhydrous eutectic gel that resists dehydration, thereby ensuring long-term operational stability. By optimizing both the device structure consisting of a fluorinated acrylate (FA)-Ecoflex bilayer with charge-trapping characteristics and the EWCI conditions, efficient charge injection and triboelectric output enhancement were achieved on stretchable and hydrogel-integrated materials. This optimization yielded a peak open circuit voltage (V_oc) of 207.9 V and a transferred charge (Q) of 88.8 nC (3 and 20 times larger respectively than pre-optimized values) when applying a bias voltage up to -2000 V for 30 min. The peak V_oc only decreases by 16% after heating at 150 °C for 1 h, by 25% after exposure to 60% relative humidity for 1 h, and by 22% after 5000 contact-separation cycles, indicating excellent endurance and long-term durability. Subsequently, EWCI was applied to a wearable hydrogel-based charge-trapping TENG (HCTEG) for efficient energy harvesting from body movements and reliable electrophysiological signal monitoring. This capability was demonstrated by charging a capacitor of 0.47 μF from 0 to 20 V in only 228 s and high-quality electrophysiological signal acquisition (signal-to-noise ratio ≥23 dB).