Flexible composite thermal energy harvester using piezoelectric PVDF polymer and shape memory alloy

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 mm3 (post-stamp size) can harvest an energy density of 0.41 mJ/cm3 per event, i.e. a temperature variation of 20°C. The harvester can directly power a light-emitting diode (LED) without any storage unit. The use of PVDF quadruples the energy, compared to previously reported harvesters based on PZT-fiber composites.