Triaxial braided piezo fiber energy harvesters for self-powered wearable technologies

Today we associate wearable technologies with electronic devices and novel approaches for powering these devices are being enabled by the advent of new piezoelectric materials and novel fabrication strategies. Mechanical energy harvesters are needed for such diverse applications as self-powered wireless sensors, structural and human health monitoring systems, and cheaply harvesting energy from human movements. Herein, we demonstrate novel triaxial braided PVDF yarn harvesters that piezoelectrically convert tensile mechanical energy into electrical energy. Compressing or bending braided PVDF yarns generated a maximum output voltage of 380 mV and a power density of 29.62 μW cm-3 which is ∼1559% higher than previously reported for piezoelectric textiles. It is found that the developed triaxial energy generator exhibits significantly higher sensitivity by a factor of 4 compared with the PVDF energy generator. Unlike other piezoelectric harvesters, the triaxial braided PVDF yarn achieves tensile energy harvesting and shows extreme durability which enables cycling with up to 50% strain for thousands of cycles with no changes in its performance. The production process is compatible with industrial, large-scale textile manufacturing and can be used for a variety of potential applications such as wearable electronic systems and energy harvesters charged from everyday body movements.