Exceeding milli-watt powering magneto-mechano-electric generator for standalone-powered electronics

In contrast to typical magnetic energy generators that use electromagnetic induction, which are bulky and have low generation efficiency under small magnetic fields at low frequency, magneto-mechano-electric (MME) generators utilizing the magnetoelectric (ME) coupling effect and magnetic interactions are considered promising candidates. MME generators will serve as a ubiquitous autonomous energy source converting stray magnetic noise to useful electric energy for applications in wireless sensor networks (WSN) for the Internet of Things (IoT) and low-power-consuming electronics. The key component in a MME generator is the ME composite consisting of piezoelectric and magnetostrictive materials, which elastically couples the electric and magnetic behaviour of the respective constituent. Here, we report a MME generator consisting of a crystallographically oriented Pb(Mg_1/3Nb_2/3)O₃-Pb(Zr,Ti)O₃ piezoelectric single crystal macro-fibre composite and a highly textured magnetostrictive Fe-Ga alloy, which exhibits an exceptionally high rectified DC output power density of 3.22 mW cm^-3. The large energy generation in this structure is ascribed to the coupling between the strong anisotropic properties of the piezoelectric single crystal fibres and textured Fe-Ga magnetostrictive alloy. A smart watch with IoT sensors was driven by the MME generator under a 700 μT magnetic field.