The field of energy textiles is growing but continues to face two main challenges: (1) flexible energy storage does not yet exist in a form that is directly comparable with everyday fabrics including their feel, drape and thickness, and (2) in order to produce an “energy textile” as part of a garment, it must be fabricated in a systematic manner allowing for multiple components of e-textiles to be integrated simultaneously. To help address these issues, we have developed textile supercapacitors based on knitted carbon fibers and activated carbon ink. We show capacitances as high as 0.51 F cm⁻² per device at 10 mV s⁻¹, which is directly comparable with those of standard activated carbon film electrodes tested under the same conditions. We also demonstrate the performance of the device when bent at 90°, 135°, 180° and when stretched. This is the first report on knitting as a fabrication technique for integrated energy storage devices.

One of the major challenges faced by passive on-body wireless Internet-of-Things sensors is the absorption of radiated power by tissues in the human body. We present a batteryless, wearable knitted ultrahigh frequency (UHF, 902-928 MHz) radio frequency identification compression sensor (Bellypatch) antenna and show its applicability as an on-body respiratory monitor. The antenna radiation efficiency is satisfactory in both free-space and on-body operations. We extract radio-frequency (RF) sheet resistance values of three knitted silver-coated nylon fabric candidates at 913 MHz. The best type of fabric is selected based on the extracted RF sheet resistance. Simulated and measured performance of the antenna confirm the suitability for on-body applications. The proposed Bellypatch antenna is used to measure the breathing activity of a programmable infant patient emulator mannequin (SimBaby) and a human subject. The antenna is highly sensitive to respiratory compression and relaxation. Fluctuations in the backscatter power level/received signal strength indicator in both cases range from 6 to 15 dB. The improved on-body read range of the proposed sensor antenna is 5.8 m, about ten times higher than its predecessor wearable knitted strain sensing Bellyband antenna (0.6 m). The maximum simulated specific absorption rate on a human torso model is 0.25 W/kg, lower than the maximum allowable limit of 1.6 W/kg.