Evaluation of vibrational PiezoMEMS harvester that scavenges energy from a magnetic field surrounding an AC current-carrying wire

This paper reports on a low-frequency vibrational piezoelectric energy harvester that scavenges energy from a wire carrying an ac current. The harvester is described, fabricated, and characterized. The device consists of a silicon cantilever with an integrated piezoelectric capacitor and a proof-mass that incorporates a permanent magnet. When brought close to an ac current carrying wire, the magnet couples to the ac magnetic field from a wire, causing the cantilever to vibrate and generate power. The device was fabricated from a silicon-on-insulator substrate using microelectromechanical systems (MEMS) technology. The charge generating capacitor uses a CMOS compatible aluminum nitride piezoelectric material and fabrication process. The device uses a commercial neodymium iron boron permanent magnet that is post-fabrication assembled with the device. The measured average power dissipated across an optimal load of 2 M was 1.5 μW. This was obtained by exciting the device into mechanical resonance with a peak displacement of 3 mm using the electro-magnetic field from a 2-A source current. The measurements also reveal that the device’s electrical response is nonlinear due to mechanical nonlinearity of the device. In addition, bandwidth broadening by 250% is demonstrated by means of vibro-impact approach.