Wearable bistable triboelectric nanogenerator for harvesting torsional vibration energy from human motion

It is ubiquitous for torsional vibration of joint in human motion. However, it is difficult to harvest low-frequency torsional vibration energy from human motion using conventional triboelectric nanogenerators (TENGs). Herein, we propose a wearable bistable triboelectric nanogenerator (WBTENG) with a bistable stiffness feature, which enables high-efficiency torsional vibration energy harvesting from human motion. The prototype of the WBTENG is fabricated to test the electrical performance of the WBTENG. The dependencies of the electrical performance of the WBTENG on dynamic behaviors are investigated. Subsequently, the experiments are carried out to investigate the output voltages under different excitation frequencies, the output power varying with the load resistances and the durability of the WBTENG. In addition, the effect of the excitation amplitude on the electrical output performance of the WBTENG is investigated in detail. The bistable mechanism of the WBTENG is proved to switch the motion pattern between interwell and intrawell oscillations. The peak power is found to reach the highest value of 3.39 mW at 3 Hz with the resistance of 90 MΩ when the WBTENG exhibits interwell oscillation. Moreover, the WBTENG can power a light-emitting diode (LED) array and drive a temperature sensor under human motions. Therefore, the WBTENG can harvest torsional vibration energy efficiently from human motion.