A gullwing-structured piezoelectric rotational energy harvester for low frequency energy scavenging

A gullwing-structural piezoelectric energy harvester mainly consisting of two typical nonlinear buckled-bridges is proposed to effectively scavenge low-frequency rotational kinetic energy based on a gear mechanism induced interwell oscillation. A natural buckled piezoelectric unit and a flexible polymer substrate are used for the buckled-bridge. A thinned bulk lead zirconate titanate ceramic is employed for the piezoelectric layer in consideration of its excellent electromechanical factor. The presented harvester can generate a peak open-circuit voltage of 20 V at a rotational frequency of 7.8 Hz, which has a low dependence on the applied frequency. A 100 μF capacitor reaches a charging voltage of 14.7 V after 38 s and is saturated at 16.05 V for 122 s. Through the power management circuit, the harvester generates an output power of 0.4 mW and the effective power density of 6.54 μW mm−3 at the low rotational frequency. These results indicate that this strategy is promising for self-powered sensors, especially at changeable and low-frequency ambient, such as tire pressure monitoring.