A multi-folded-beam piezoelectric energy harvester for wideband energy harvesting under ultra-low harmonic acceleration

In this paper, a multi-folded-beam piezoelectric energy harvester (MFB-PEH) was proposed for low-power energy harvesting applications in wide frequency band, low frequency, and low amplitude vibration environments. The MFB-PEH consists of one traditional main beam and two new additional L-shaped wing beams, which are designed to improve the frequency bandwidth and harvest low frequency, low amplitude ambient vibration energy. Firstly, finite element method (FEM) was used to search for the optimal design that can make the operational bandwidth broader and yield the maximum power output. The experimental results reveal that the optimized MFB-PEH has three resonance frequencies in the ambient frequency range from 9 Hz to 20 Hz, which can broaden the operation bandwidth of the harvester. It is significant that the MFB-PEH device, excited at an ultra-low harmonic acceleration of 0.2 m/s2, generates a much higher output power of 29.0μW, four times higher than other multi-beam devices at the low frequency of ∼9.2 Hz. Finally, a packaged MFB-PEH was adopted to harvest the energy generated by human motion, where the MFB-PEH can generate a high voltage of 24 Vp−p when walking and 55 Vp−p when running. Our work has confirmed that the MFB-PEH is a good potential generator in wide frequency band, low frequency, and low amplitude vibration environments.