RF-powered wearable energy harvesting and storage module based on e-textile coplanar waveguide rectenna and supercapacitor

Wagih, M. , Hillier, N., Yong, S., Weddell, A. S. and Beeby, S. (2021) RF-powered wearable energy harvesting and storage module based on e-textile coplanar waveguide rectenna and supercapacitor. IEEE Open Journal of Antennas and Propagation, 2, pp. 302-314. (doi: 10.1109/OJAP.2021.3059501)

Abstract

This paper presents a high-efficiency compact ( 0.016λ20 ) textile-integrated energy harvesting and storage module for RF power transfer. A flexible 50 μm -thick coplanar waveguide rectenna filament is integrated with a spray-coated supercapacitor to realize an “e-textile” energy supply module. The meandered antenna maintains an S11<−6 dB inside and outside the fabric and in human proximity with a 2.3 dBi gain. The rectifier achieves a peak RF-DC efficiency of 80%, across a 4.5 kΩ load, and a 1.8 V open-circuit voltage from −7 dBm. The supercapacitor is directly spray-coated on a cotton substrate using carbon and an aqueous electrolyte. When connected to the supercapacitor, the rectifier achieves over an octave half-power bandwidth. The textile-integrated rectenna is demonstrated charging the supercapacitor to 1.5 V (8.4 mJ) in 4 minutes, at 4.2 m from a license-free source, demonstrating a significant improvement over previous rectennas while eliminating power management circuitry. The integrated module has an end-to-end efficiency of 38% at 1.8 m from the transmitter. On-body, the rectenna’s efficiency is 4.8%, inclusive of in-body losses and transient shadowing, harvesting 4 mJ in 32 seconds from 16.6 μW /cm 2 . It is concluded that e-textile rectennas are the most efficient method for powering wearables from μW /cm 2 power densities.

• Item Type: Articles
• Additional Information: This work was supported in part by the European Commission through the Project EnABLES, funded under H2020-EU.1.4.1.2 under Grant 730957, and in part by U.K. Engineering and Physical Sciences Research Council (EPSRC) under Grant EP/P010164/1 and Grant EP/L016818/1.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Wagih, Dr Mahmoud
• Authors: Wagih, M., Hillier, N., Yong, S., Weddell, A. S., and Beeby, S.
• College/School: College of Science and Engineering > School of Engineering > Systems Power and Energy
• Journal Name: IEEE Open Journal of Antennas and Propagation
• Publisher: IEEE
• ISSN: 2637-6431
• ISSN (Online): 2637-6431
• Published Online: 16 February 2021
• Copyright Holders: Copyright © 2021 The Author(s)
• First Published: First published in IEEE Open Journal of Antennas and Propagation 2: 302-314
• Publisher Policy: Reproduced under a Creative Commons licence