Enhanced Power Density by Resonant Frequency Optimization in Magneto‐Mechano‐Electric Generator for Multifunctional Wireless Sensor System

Harvesting electrical energy from stray magnetic fields around the power cable is attractive in developing sustainable power sources for wireless sensor network. Magneto-mechano-electric (MME) generators, consisting of cantilevered magnetoelectric (ME) composite with permanent magnet mass, are promising for efficiently converting low-frequency stray magnetic fields into electrical energy. However, the power density needs further improvement for practical applications. Here, enhanced power density in MME generator is reported by optimizing the resonant frequency via structural optimization. This enhancement is ensured by manipulating the length ratio of the piezoelectric with regards to that of the magnetostrictive materials, as well as optimizing the total thickness of the ME composite, both of which are essential for matching the resonant frequency at 50 Hz. High output power density of 0.137 mW_RMS cm^-3 Oe^-2 under a small magnetic field of 0.5 Oe is achieved at 50 Hz in the MME generator. Meanwhile, the optimized MME generator can electrically power the multifunctional IoT sensors and wireless communication systems, by harvesting the uniform magnetic field as well as the stray magnetic field energy around the power cables of household appliances. The MME generator with high energy density shows great potential for the applications in self-powered wireless sensor network.