Passive power management for triboelectric nanogenerators in sub-microwatt applications

Triboelectric nanogenerators (TENGs) have been regarded as a promising enabling technology for self-powered applications. However, their inherent characteristics, such as high internal impedance and high output voltage, not only make them unsuitable to be used as a direct power source but also create substantial challenges in power management for low-power applications. To date, effective power management systems have not been available for sub-microwatt applications. In this study, we propose a passive power management system for such extremely low-power scenarios. The system can effectively condition the electricity generated by a TENG into a form compatible with standard electronic devices, which can then be stored on an energy storage device. We demonstrate that for TENGs using a liquid metal drop, the power management system can transfer up to 85% of the electricity generated to the storage when the power output of the TENG is below 1 μW. For TENGs using a water drop, the energy transfer efficiency can reach a remarkably high level of 80% when the TENG harvests as low as 38 nJ of energy per cycle.