Molecular level manipulation of charge density for solid-liquid TENG system by proton irradiation

With the rapid development of flexible electronics, methods for improving the performance of self-powered triboelectric nanogenerators (TENGs) have been in continuous demand. Due to its low density, and excellent physical and chemical properties, polyimide (Kapton or PI) was applied widely in space. As space materials such as spacecraft, PI will be irradiated by protons and other charged particles during the long-term service in space. In this study, we proposed a surface modification method using low-energy proton irradiation for tuning the internal chemical structure and functional groups at the molecular level and improving TENG performance. A solid-liquid dual-phase TENG using gallium–indium (Ga-In) eutectic alloy as liquid-phase friction material and PI as solid-phase friction material was successfully prepared. Systematic studies about the PI performance induced by proton irradiation parameters can bring insights into the interaction between the density of unsaturated bonds and electrification performance. The effect mechanism of proton irradiation on TENG property was elucidated. Compared with the initial state, the open-circuit voltage of the solid-liquid dual-phase TENG based on Ga-In eutectic alloy increased by about 57.4 % to 107.5 V, the short-circuit current density was 2.02 μA·cm−2, and the charge transfer density was 103.22 μC·m−2. Astonishingly, proton irradiation, which normally has adverse effects on devices, achieved a significant improvement in solid-liquid dual-phase TENG performance. High charge density is the key factor affecting the performance of TENG devices, and this study revealed a different approach for modifying the characteristics of solid-liquid dual-phase TENG. On the basis of the results of this study and through a series of possible breakthroughs in outer space and other environments, the reliable power supply by Ga-In eutectic alloy integrated TENG, under the presence of radiation, can be realized.