Exceeding 50 mW RMS-Output Magneto-Mechano-Electric Generator by Hybridizing Piezoelectric and Electromagnetic Induction Effects

A magneto-mechano-electric (MME) generator with root mean square (RMS) output exceeding 50 mW is demonstrated by integration of a piezoelectric Pb(Mg_1/3Nb_2/3)O₃-Pb(Zr,Ti)O₃ (PMN-PZT) single crystal and an electromagnetic induction structure to convert a gentle alternating current magnetic field into electricity to operate a high-power consumption multi-functional Internet of Things (IoT) environmental monitoring system. The 2nd resonance bending mode at the cantilever-type hybrid MME generator enabled much higher output power than the conventional 1st resonance mode, which is theoretically investigated by a finite element analysis. The hybridized MME generator can generate a total RMS output power of 60 mW since the output power of the piezoelectric and electromagnetic induction parts is 26.7 and 33.3 mW, respectively, by a magnetic field of 7 Oe at the 2nd harmonic bending mode. The hybrid MME generator is employed to irradiate a red laser as well as to fully charge a commercial 280 mAh LiFePO₄ battery. Finally, a self-powered multi-functional IoT environment monitoring system is constructed by integrating the hybrid MME generator, a power management circuit, and a wireless multiple sensing modules. The remarkable output power from the hybridized MME generator enabled the continuous sensing of nine types of ambient information and subsequent transmission of the measured data to a smartphone.