Despite an increasing interest in wearable wireless power transmission (WPT), until now, wearable antennas have been unable to simultaneously harvest from near-field resonant and far-field radiative ...WPT. Here, a dual-port antenna is proposed, integrating an inductive coil with a broadband monopole for near- and far-field wearable WPT. The coil acts simultaneously as a High Frequency (HF) near-field power receiver and an Ultra-High Frequency (UHF) resonator, enabling the miniaturization of the enclosed broadband monopole, both fabricated using all-textile conductors. On-body, the antenna maintains a 10 dB return loss over a measured 135% fractional bandwidth while maintaining compactness (<inline-formula> <tex-math notation="LaTeX">0.312\times 0.312\lambda ^{2} </tex-math></inline-formula>). The antenna is substrate-independent and is demonstrated on two textile substrates with different dielectric properties and thicknesses. In far-field mode, the rectenna maintains over 40% efficiency from sub-1 <inline-formula> <tex-math notation="LaTeX">\mu \text{W} </tex-math></inline-formula>/cm 2 power densities. In the near-field, a WPT efficiency up to 80% can be achieved. The simulated Specific Absorption Rate (SAR) shows up to 40 and 20 dBm power reception for HF and UHF operation, respectively, without exceeding the 1.7 W/kg limit. The far-field wearable rectenna is demonstrated powering a Bluetooth Low Energy node using a BQ25504 DC-DC converter from a best-in-class low power density of 0.88 and <inline-formula> <tex-math notation="LaTeX">0.55~\mu \text{W} </tex-math></inline-formula>/cm 2 on-body and in-space, respectively.
Electronically active yarn (E-yarn) pioneered by the Advanced Textiles Research Group of Nottingham Trent University contains a fine conductive copper wire soldered onto a package die, ...micro-electro-mechanical systems device or flexible circuit. The die or circuit is then held within a protective polymer packaging (micro-pod) and the ensemble is inserted into a textile sheath, forming a flexible yarn with electronic functionality such as sensing or illumination. It is vital to be able to wash E-yarns, so that the textiles into which they are incorporated can be treated as normal consumer products. The wash durability of E-yarns is summarized in this publication. Wash tests followed a modified version of BS EN ISO 6330:2012 procedure 4N. It was observed that E-yarns containing only a fine multi-strand copper wire survived 25 cycles of machine washing and line drying; and between 5 and 15 cycles of machine washing followed by tumble-drying. Four out of five temperature sensing E-yarns (crafted with thermistors) and single pairs of LEDs within E-yarns functioned correctly after 25 cycles of machine washing and line drying. E-yarns that required larger micro-pods (i.e., 4 mm diameter or 9 mm length) were less resilient to washing. Only one out of five acoustic sensing E-yarns (4 mm diameter micro-pod) operated correctly after 20 cycles of washing with either line drying or tumble-drying. Creating an E-yarn with an embedded flexible circuit populated with components also required a relatively large micro-pod (diameter 0.93 mm, length 9.23 mm). Only one embedded circuit functioned after 25 cycles of washing and line drying. The tests showed that E-yarns are suitable for inclusion in textiles that require washing, with some limitations when larger micro-pods were used. Reduction in the circuit's size and therefore the size of the micro-pod, may increase wash resilience.
Wearable devices are ideal for personalized electronic applications in several domains such as healthcare, entertainment, sports and military. Although wearable technology is a growing market, ...current wearable devices are predominantly battery powered accessory devices, whose form factors also preclude them from utilizing the large area of the human body for spatiotemporal sensing or energy harvesting from body movements. E-textiles provide an opportunity to expand on current wearables to enable such applications via the larger surface area offered by garments, but consumer devices have been few and far between because of the inherent challenges in replicating traditional manufacturing technologies (that have enabled these wearable accessories) on textiles. Also, the powering of e-textile devices with battery energy like in wearable accessories, has proven incompatible with textile requirements for flexibility and washing. Although current e-textile research has shown advances in materials, new processing techniques, and one-off e-textile prototype devices, the pathway to industry scale commercialization is still uncertain. This paper reports the progress on the current technologies enabling the fabrication of e-textile devices and their power supplies including textile-based energy harvesters, energy storage mechanisms, and wireless power transfer solutions. It identifies factors that limit the adoption of current reported fabrication processes and devices in the industry for mass-market commercialization.
High-quality films of bismuth antimony telluride were synthesized by electrodeposition from nitric acid electroplating baths. The influence of a surfactant, sodium ligninsulfonate, on the structure, ...morphology, stoichiometry, and homogeneity of the deposited films has been investigated. It was found that addition of this particular surfactant significantly improved the microstructural properties as well as homogeneity of the films with a significant improvement in the thermoelectric properties over those deposited in the absence of surfactant. A detailed microprobe analysis of the deposited films yielded a stoichiometric composition of Bi0.35Sb1.33Te3 for the films electrodeposited in the absence of surfactant and a stoichiometry of Bi0.32Sb1.33Te3 for films deposited in the presence of surfactant.
Electronic textiles (e-textiles) development has been attracting significant research interest over the past two decades, especially in the field of wearable electronics. Fabric based flexible ...batteries are an attractive solution to the challenge of powering e-textiles. This work presents a simple and scalable textile primary battery, produced via a low-cost screen-printing manufacturing process. The device architecture is purposefully simple, based on a standard aluminum-silver redox reaction and a salt bridge. The battery as manufactured is inactive and requires the addition of water to be activated, and it can therefore be classified as a reserve battery. The battery is suitable for long-term storage, having negligible self-discharge rates. Initial batteries achieved a total area capacity of <inline-formula> <tex-math notation="LaTeX">101.6~\mu </tex-math></inline-formula>Ah/cm 2 and an energy density of 2.178 mWh/cm 3 above 0.8 V. Further refinements of the battery include the inclusion of a novel membrane separator within the woven cotton textile layer and blending the metal salts with polyvinyl alcohol to reduce the number of textile layers. This optimization resulted in an improved performance of <inline-formula> <tex-math notation="LaTeX">166.8~\mu </tex-math></inline-formula>Ah/cm 2 in area capacity and 3.686 mWh/cm 3 in energy density above 0.8 V. This work has demonstrated the feasibility of an aluminum-silver reserve textile battery and demonstrates a novel method for printing a phase inversion membrane separator into the textile. Following an encapsulation process, this flexible textile battery can be easily integrated into a standard woven textile, providing a robust, lightweight and flexible power supply.
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