Enhancing weak magnetic field MME coupling in NdFeB magnet/piezoelectric composite cantilevers with stress concentration effect

In this work, we theoretically and experimentally report a NdFeB magnet/piezoelectric composite cantilever with varying stiffness for enhancing magneto-mechano-electric (MME) coupling under weak AC magnetic field Hac excitation. Measurement results show that the MME composite cantilever can produce a relatively high peak-peak output power of 12.8 mW and a peak-peak current of 0.735 mApp under Hac = 7 Oe at a resonance frequency of 36 Hz. Even when Hac is as low as 0.2 Oe, equivalent to the level of the earth magnetic field, it can still drive 4 LED lighting. The obtained results are obviously superior to previous reports, confirming the MME cantilever harvester has potential to harvest the stray magnetic field energy from electrical power cables for continuously powering wireless sensor networks.