Multiple-coupling optimization strategy for significantly enhancing the output power density of a compact magneto-mechano-electric energy harvester

A magneto-mechano-electric-energy harvester (MME-EH) is considered a promising candidate for powering the “Internet of Things” (IoT) devices by capturing power-frequency magnetic fields, which are ubiquitous in modern infrastructure. However, further reduction in size of conventional MME-EHs has encountered considerable challenges due to the insufficient MME coupling efficiency of cantilever structures with limited space. We report an optimization strategy for significantly enhancing the output power density of MME-EHs, realized by strengthening magneto-mechanical, mechanical, and electromechanical couplings by adjusting the relative position of the neutral axis and flexural rigidity of piezoelectric/elastic phases. Experimentally, the optimized MME-EH with a compact volume of 0.97 cm³ achieved a record-high output power density of 0.73 mW cm⁻³ Oe⁻² under a weak magnetic field of 1 Oe at 50 Hz, representing a 124% enhancement compared with that of previously reported MME-EHs. The underlying mechanisms were revealed theoretically by multi-field coupled behavior analysis based on a finite element analysis model and a two-degree-of-freedom equivalent spring-mass model. The power supply capability of the proposed MME-EH was demonstrated in a wireless sensor network (WSN) for smart grids, which paves the way for potential applications in self-powered large-scale WSNs.