A Millimeter Scale Piezoelectric Receiver with Sub-Milliwatt Output for Ultrasonic Wireless Power Transfer in Water

摘要

We here investigate the power conversion efficiency (PCE) of a millimeter scale piezoelectric receiver (PZT-5H) characterized in water for the first time for ultrasonic wireless power transfer (UWPT). This study targets WPT applications where the energy harvester must fit within a is tightly constrained space located far from the source (very large depth to aperture ratio) such as in the case for deep biomedical implants. Measurements were carried in water, at a depth of 50 mm (depth to aperture ratio of 50:1), to mimic the dielectric property of soft tissues more closely. Without impedance matching, the receiver can harvest 0.66 mW ($3 mathrm{k}Omega$ terminal load) from an acoustic source intensity of 7.2 mW/mm^{2 (close to the FDA limit for diagnostic ultrasound). We show that with adaptive transducer to load matching, an overall efficiency of 14% is attainable.}