A novel flexible composite thermal energy harvester is presented, which couples pyroelectric and piezoelectric effects of polyvinylidene fluoride (PVDF) with shape memory effect of a TiNiCu alloy. The harvester combines superior flexibility of PVDF with large temperature-induced strain of the shape memory alloy (SMA) to harvest small and quasi-static temperature variations. The composite with a volume of 27.5 mm 3 (post-stamp size) can harvest an energy density of 0.41 mJ/cm 3 per event, i.e. a temperature variation of 20°C. The harvester can directly power a lightemitting diode (LED) without any storage unit. The use of PVDF quadruples the energy, compared to previously reported harvesters based on PZT-fiber composites.

Abstract:In this paper, we compare different techniques to manufacture high-performance miniature disks of Terfenol-D aiming at self-powered IoT sensors. To reach large in-plane magnetostriction while maintaining low driving field, microstructure engineering is essential. This work covers monocrystalline, polycrystalline and hot-pressed powder materials whose performances are analyzed. A "performance phase diagram per technique" is reported at the end.