This paper presents a high-efficiency compact ( $0.016\lambda _{0}^{2}$ ) textile-integrated energy harvesting and storage module for RF power transfer. A flexible 50 $\mu \text{m}$ -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 $S_{11}< -6$ 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 $\text{k}\Omega $ 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 $\mu \text{W}$ /cm ² . It is concluded that e-textile rectennas are the most efficient method for powering wearables from $\mu \text{W}$ /cm ² power densities.

In this paper, a novel multi-layered microstrip line with built-in parallel-plate capacitors is proposed for DC-blocking applications, with its transmission characteristics measured up to 50 GHz. The microstrip lines are fabricated via screen printing directly onto polyurethane films laminated on standard textile substrates which would otherwise be unsuitable for printing. Compared to a standard microstrip line on the same substrate, the proposed 10 cm-long line on felt (with an embedded 44 pF capacitance) suffers from less than 0.1 dB higher insertion loss up to 4 GHz. Furthermore, varying the overlapping length of the lines and hence the capacitance enables the realization of DC blocking and $-$ 3 dB high-pass filtering with pass-bands starting between 88 MHz and 1.2 GHz. This is achieved without altering the cut-off frequency of the microstrip line’s mode-free propagation, measured up to 50 GHz, exhibiting a low attenuation of 0.32 dB/mm at 50 GHz on a felt fabric substrate. Compared to a lumped capacitor, the proposed microstrip-embedded printed capacitor demonstrates a significant improvement in mechanical reliability, withstanding over 10,000 bending cycles, and RF power handling with under 6 $^{\circ }$ C temperature rise at 1 W. The lines are fabricated on two textile substrates and their transmission characteristics were measured up to 50 GHz, which represents the highest frequency characterization of textile-based lines to date, demonstrating a stable group delay and insertion losses. Based on the proposed multi-layered integration method, low-cost screen-printed microstrip-embedded capacitors on textiles can be used for microwave applications up to mmWave bands.

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 $101.6~\mu $ 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 $166.8~\mu $ 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.

The importance of magnetic cleanliness and inflight compensation to account for fluctuations in magnetic field is a recognized concern within the space industry. Their effects must be considered, minimized, and where necessary compensated throughout the development of any spacecraft, their subsystems, and while in flight. This is just as true within the context of the laser interferometer space antenna pathfinder mission, where sensitive gravitational wave telemetry systems are vulnerable to magnetic disturbances. In collaboration with the Science and Technology Facility Council, Rutherford Appleton Laboratory, Bartington Instruments, and the National Physical Laboratory (NPL), a compact low-noise gradiometer was developed under European Space Agency contract reference AO/1-6085/09/NL/AF. Such a versatile device will be used on the ground to assess the magnetic cleanliness of spacecraft and also inflight, to monitor changes in the local magnetic field. This paper introduces the capabilities developed by NPL, specifically for the calibration of the compact low-noise fluxgate gradiometer. The procedures used to test and calibrate the novel gradiometer will be discussed in detail, including a range of Helmholtz coils, gradient coils (used to generate known diagonal and off-diagonal gradients), and shielding techniques. These technologies were combined to establish key parameters, such as low frequency noise, offset, gain and gradient sensitivity, with specific attention given to the off-diagonal terms of the gradient tensor matrix.