Piezoelectric shell structures as wearable energy harvesters for effective power generation at low-frequency movement

This paper discusses a flexible energy harvester that consists of a polyvinylidene fluoride film attached to a curved substrate in a shell shape for harvesting energy from human motion. The proposed harvester effectively converts mechanical energy into electrical energy during the fast state transition of the shell structure. The results of an experiment demonstrated that shell structures with various curvatures produce high output potential and consequently offer high output power in comparison to a simple flat structure. The single shell structure generates an output power of 0.87 mW at a folding angle of 80° and a folding and unfolding frequency of 3.3 Hz. In addition, fabric with embedded piezoelectric shell structures was designed as an energy harvester in a wearable platform. The fabric, worn on the elbow joints and fingers, generates a high output power of 0.21 mW in spite of slow and irregular motion.