Stretchable and transparent PVA/Borax organohydrogel-based triboelectric nanogenerator for self-powered wearables and human–machine interfaces

Abstract

Highly stretchable triboelectric nanogenerators (TENGs) are indispensable for conformal energy harvesting and self-powered sensing. The hydrogel-based TENGs have demonstrated encouraging performance in the fabrication of flexible and transparent devices. Here, we introduce a transparent and stretchable conductive organohydrogel which was synthesized in a water/glycerol co-solvent system via cross-linking of poly(vinyl alcohol) (PVA) and borax. The electrical conductivity of the PVA/borax organohydrogel can be tuned over a broad range simply by adjusting the borax concentration. The prepared organohydrogel can be utilized as a resistance sensor to monitor human motions. A single-electrode TENG was developed by employing the PVA/borax organohydrogel as an electrode and silicone rubber as a triboelectric layer. An optimally formulated organohydrogel-based TENG (OH-TENG) delivers a peak-to-peak voltage of approximately 500 V, a short-circuit current of 3.0 µA, and a transferred charge of 145 nC under a 3.0 Hz mechanical excitation. Demonstrations show that the device rapidly charges an electrolytic capacitor, effortlessly illuminates a string of green LEDs, and powers portable electronics. When interfaced with Darlington transistors and relay modules, the OH-TENG can reliably switch external circuits on and off. It has also been integrated with a Bluetooth oscilloscope module, enabling real-time monitoring of human movements. These results highlight its potential applications in human–machine interfaces and safety systems. This study elucidates how organohydrogel properties govern the performance of OH-TENGs and provides a general blueprint for designing next-generation, highly stretchable TENGs.