Wearable E-Textile Wireless RF Power Supply based on a Textile Supercapacitor and a Flexible Rectenna Filament

Abstract

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 spraycoated 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 fourbranch 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.

Concomitance of radio frequency energy harvesting and wearable devices: A review of rectenna designs

“…The single band rectennas used for RF energy harvesting are usually easy to design. 33 Depicted the model of a single band wearable energy harvester which was a textile-based and a charge accumulator module as shown in Figure 3. A supercapacitor (7.1 mF) was spray-coated and integrated as a battery unit.…”

“…F I G U R E 3 Prototype on textile substrate 33 The authors presented a rectenna that operated at ultra high frequency (UHF) band (0.8 and 0.9 GHz) in reference 40. Figure 10A depicts a patch antenna made from a non-woven textile that was conductive, on a substrate of pile and denim.…”