A Hybrid Piezoelectric Structure for Wearable Nanogenerators

The concept of human-motion-based energy harvesting has huge technological interest in accordance with the growing popularity of portable smart electronics. It is becoming more feasible, due to advanced research in nanoelectronics, to operate at an extremely low power consumption, so that energy scavenged from the environment may be suffi cient to meet the working mode. [ 1–3 ] Solar and thermal energies are the most-common and feasible sources of energy to be scavenged from our surroundings. However, these types of energy are time and location dependent. Especially for personal electronics, mechanical energy is the most-likely reliable and independent energy source, since human activities are based mostly on mechanical movement, regardless of environment. Harvesting energy from body motion or human activity has a strong potential, which can untie modern personal life from the messy connections of wires for electric power supply. According to such a concept, nanowirebased nanogenerators (NGs) built on textile fi bers or solid substrates have been demonstrated for the harvesting of mechanical energy produced by the friction-motion of two fi bers or ultrasonic waves. [ 4 , 5 ] Until now, for scavenging of energy from mechanical movement, especially human activity, it has been important to explore wearable and sustainable technologies that work at low frequencies and at various amounts/directions of deformation, and that are based on fl exible and durable materials. Herein, we present a simple but practical and durable approach that converts low-frequency ( < 1 Hz) mechanical activity into electricity using hybrid piezoelectric materials. Our device was composed of zinc oxide nanowires (NWs) and poly(vinylidene fl uoride) (PVDF) polymer around a conducting fi ber, which is a unique hybridization of two piezoelectric materials. The zinc oxide NWs served as a piezoelectric-potential