Wearable e-textile wireless RF power supply based on a textile supercapacitor and a flexible rectenna filament

Sustainable battery-free operation is a requirement for wearable electronic textiles. This work presents a complete wearable textile-based radio frequency energy harvester and an energy storage module. The rectifying-antenna (rectenna) receives incident sub-1 GHz RF power from a license-free transmitter and converts it to DC with up to 90% efficiency and 8 V DC output from under 4 mW of RF power. A spray-coated in-house textile 7.1 mF supercapacitor is integrated as an energy storage unit. Electrochemical Impedance Spectroscopy has been used to characterize the supercapacitor's impedance and a four-branch circuit model has been obtained. The 7.1 mF textile supercapacitor has been demonstrated charging to 1 V (3.55 mJ) in under 11 seconds at 1.2 m separation from a wireless power source, demonstrating over 15% end-to-end efficiency, the highest charging efficiency of a textile supercapacitor from an integrated flexible energy source