A speed-amplified tri-stable piezoelectric-electromagnetic-triboelectric hybrid energy harvester for low-frequency applications

This work proposes a new speed-amplified multi-stable tri-hybrid energy harvesting technique via the multi-stable nonlinearity enhanced frequency up-conversion and rack-pinion mechanisms to efficiently harness structural and biomechanical vibration energy. In the present design, two frequency up-conversion piezoelectric generators, an array-type electromagnetic generator and a sliding-mode triboelectric nanogenerator are integrated together to form a compact and interactive system. By utilizing the rack-pinion mechanism, the relative speed between the stators and the translators of the electromagnetic and triboelectric generators are both doubled. Meanwhile, the process of frequency up-conversion in the piezoelectric generators is also doubled per each cycle. This results in better performance under wideband and low-frequency vibration sources. For verification, a prototype of this design is tested by mechanical excitations and body-induced motions. In the shaker test, the prototype can generate a peak output power of 446.16 mW under an optimal resistance load, resulting in a normalized power density of 4.20 mW cm^–3 g^–2 at 5 Hz under 1 g. The prototype also exhibits exceptional performance under various human motion tests, it can drive 600 commercial light-emitting diodes simultaneously. Using a commercial DC/DC voltage regulator circuit, the proposed harvester can serve as a universal power source to charge commercial electronic devices, including smartphones and GPS sensors. The present design shows great potential as a sustainable power source for wearable/portable electronics as well as wireless monitoring systems.