Harvesting ultralow frequency (< 1 Hz) mechanical energy using triboelectric nanogenerator

Mechanical energy has been widely harvested to meet the increasing worldwide energy demands, especially propelled by the breakthrough of Triboelectric nanogenerator (TENG). Although extensive progresses have been achieved in the development of TENGs to harvest low-frequency mechanical energy, the collection of ultralow frequency mechanical energy less than 1 Hz remains challenging so far. Here we report a study on harvesting ultra-low frequency mechanical energy by TENG utilizing modulating the mechanical vibrations. An equivalent circuit model of the TENG is derived to theoretical analyze the influence of ultralow frequency mechanical energy with different vibration waveforms in energy harvesting. The theoretical model provides reasonable interpretation of the harvesting performance for ultralow frequency mechanical energy with different vibration waveforms and contact-release time, which keeps in consistency with our experimental results. By reducing the contact-release time, the collection efficiency of TENGs is significantly improved, even if the mechanical input frequency is 0.1 Hz. This work advances the deep understanding of harvesting ultralow mechanical energy using TENGs, and provides an important insight for the design of the TENGs that can harvest various mechanical energy in wide frequencies.