Multifunctional Coaxial Energy Fiber toward Energy Harvesting, Storage, and Utilization.

Fibrous energy-autonomy electronics are highly desired for wearable soft electronics, human-machine interfaces, and the Internet of Things. How to effectively integrate various functional energy fibers into them and realize versatile applications is an urgent need to be fulfilled. Here, a multifunctional coaxial energy fiber has been developed toward energy harvesting, energy storage, and energy utilization. The energy fiber is composed of an all fiber-shaped triboelectric nanogenerator (TENG), supercapacitor (SC), and pressure sensor in a coaxial geometry. The inner core is a fibrous SC by a green activation strategy for energy storage; the outer sheath is a fibrous TENG in single-electrode mode for energy harvesting, and the outer friction layer and inner layer (covered with Ag) constitute a self-powered pressure sensor. The electrical performances of each energy component are systematically investigated. The fibrous SC shows a length specific capacitance density of 13.42 mF·cm-1, good charging/discharging rate capability, and excellent cycling stability (∼96.6% retention). The fibrous TENG shows a maximum power of 2.5 μW to power an electronic watch and temperature sensor. The pressure sensor has a good enough sensitivity of 1.003 V·kPa-1 to readily monitor the real-time finger motions and work as a tactile interface. The demonstrated energy fibers have exhibited stable electrochemical and mechanical performances under mechanical deformation, which make them attractive for wearable electronics. The demonstrated soft and multifunctional coaxial energy fiber is also of great significance in a sustainable human-machine interactive system, intelligent robotic skin, security tactile switches, etc.