Asymmetric PZT bimorph cantilever for multi-dimensional ambient vibration harvesting

A vibration based piezoelectric cantilever energy harvester was investigated as a power source by generating the electricity from two-dimensional ambient vibrations (less than 1 g and 60 Hz) for mobile handsets, building automation, medical, and defense applications. The proposed energy harvester was designed and fabricated by using a bimorph lead zirconate titanate (PZT) bender and an aluminum inertial mass. In order to harvest the two dimensional vibrations, the fabricated inertial mass was asymmetrically assembled at the end of the PZT bender by adjusting the center of mass. The asymmetric inertial mass contributes to generate power from the vibration applied into the length and thickness directions of PZT bender. The fabricated bimorph PZT bender exhibited a volume of 36×10×0.72 mm3and capacitance of 7.5 nF. The fabricated device generated the maximum output power at the resonant frequency of 45 Hz and the load impedance of 100 kΩ for input vibrations in the z-axis and the x-axis. The output powers and voltages were approximately 7.5 mW and 38.5 V for the z-axis and 1.4 mW and 16.7 V for the x-axis when 10 m/s2 of acceleration was applied at its resonant frequency.