Micromachined PZT cantilever based on SOI structure for low frequency vibration energy harvesting

A PZT piezoelectric cantilever with a micromachined Si proof mass is designed and fabricated for a low frequency vibration energy harvesting application. The SiO2 layer in the SOI wafer promotes accurate control of the silicon thickness that is used as a supporting layer in the cantilever beam structure. The entire effective volume of the fabricated device is about 0.7690 mm3. When excited at 0.75g (g = 9.81 m/s2) acceleration amplitude at its resonant frequency of 183.8 Hz, the AC output measured across a resistive load of 16 kΩ connecting to the device in parallel has an amplitude of 101 mV. The average power and power density determined by the same measurement conditions are, respectively, 0.32 μW and 416 μW/cm3.