Piezoelectric Energy Harvester with Piezo-Magnet Stack for Ultrasonically-Powered Brain Implants

This paper presents a novel approach to improve the performance of Piezoelectric Energy Harvesters (PEHs) applicable to a variety of applications, e.g. biomedical implants. This is brought by stacking a magnet over the piezoelectric material, i.e. a piezo-magnet stack. Using the proposed piezomagnet stack, an improvement in the generated power on the piezoelectric receiver from ultrasonic waves is observed. This is attributed to the interaction of amplified force induced by the magnetic material and the manipulation of the polarization of the piezoelectric material making the receiver more sensitive to mechanical waves. Experimental results show an output power of up to 3.27mW when equipping a 1mm ³ Lead Zirconate Titanate (PZT4) cube as piezoelectric material with the same-size cubic Neodymium (NdFeB) magnet, which is 18% higher compared to the piezoelectric cube without the magnet. The PZT showed 13% frequency shift of the resonance frequency to a higher frequency, when it is stacked with the magnet.