Automatically switchable mechanical frequency regulator for continuous mechanical energy harvesting via a triboelectric nanogenerator

In this work, we proposed a mechanical frequency regulator (MFR) with automatic switching (AS) integrated with a triboelectric nanogenerator (ASMFR-TENG) for continuous mechanical energy harvesting of low torque irregular input energies. Our ASMFR-TENG primarily consisted of gear-trains, a spiral-spring, a blocker-stopper unit, a triboelectric nanogenerator (TENG), and a governor. The gear-train (here, gear train #1) connected to an input handle was employed to effectively harvest low torque ambient mechanical energies. The spiral-spring (here, a mainspring) was the energy-storage conversion component from which energy can be extracted in a controlled manner. Automatically switchable operation of the ASMFR-TENG was achieved through the blocker-stopper unit, where the TENG output signal was regulated through a controlled governor design. We systematically studied the influence of blocker shape and governor design parameters on the TENG output behaviors. First, we demonstrated that the regulated TENG output could be controlled in the frequency range of 19–55 Hz and in an operation time of 2.9–5.6 s by adjusting the governor design parameters. Secondly, we examined the significant effects of blocker shapes to prevent unregulated TENG output (i.e., charging times) and adjust the regulated TENG output (i.e., operation times). As a result, we greatly reduced the mainspring charging time from 13.3 s to 3.4 s, resulting in a nearly continuous cycling operation of an ASMFR-TENG. Finally, we demonstrated hands-free (i.e., automatic) operation and capacitor charging using the ASMFR-TENG based on the blocker-stopper mechanism.