In this work, two embroidered textile moisture sensors are characterized with three different conductive yarns. The sensors are based on a capacitive interdigitated structure embroidered on a cotton substrate with an embroidered conductor yarn. The performance comparison of three different type of conductive yarns has been addressed. In order to evaluate the sensor sensitivity, the impedance of the sensor has been measured by means of an LCR meter from 20 Hz to 20 kHz on a climatic chamber with a sweep of the relative humidity from 30% to 65% at 20 °C. The experimental results show a clear and controllable dependence of the sensor impedance with the relative humidity and the chosen conductor yarns. This dependence points out the optimum conductive yarn to be used to develop wearable applications for moisture measurement.

In this work, an embroidered textile moisture sensor is presented. The sensor is based on a capacitive interdigitated structure embroidered on a cotton substrate with an embroidery conductor yarn composed of 99% pure silver plated nylon yarn 140/17 dtex. In order to evaluate the sensor sensitivity, the impedance of the sensor has been measured by means of a impedance meter (LCR) from 20 Hz to 20 kHz in a climatic chamber with a sweep of the relative humidity from 25% to 65% at 20 °C. The experimental results show a clear and controllable dependence of the sensor impedance with the relative humidity. Moreover, the reproducibility of the sensor performance subject to the manufacturing process variability and washing process is also evaluated. The results show that the manufacturing variability introduces a moisture measurement error up to 4%. The washing process impact on the sensor behavior after applying the first washing cycle implies a sensitivity reduction higher than 14%. Despite these effects, the textile sensor keeps its functionality and can be reused in standard conditions. Therefore, these properties point out the usefulness of the proposed sensor to develop wearable applications within the health and fitness scope including when the user needs to have a life cycle longer than one-time use.

In this paper, the utilization of common fabrics for the manufacturing of e-textile metamaterial transmission lines is investigated. In order to filter and control the signal propagation in the ultra-high frequency (UHF) range along the e-textile, a conventional metamaterial transmission line was compared with embroidered metamaterial particles. The proposed design was based on a transmission line loaded with one or several split-ring resonators (SRR) on a felt substrate. To explore the relations between physical parameters and filter performance characteristics, theoretical models based on transmission matrices’ description of the filter constituent components were proposed. Excellent agreement between theoretical prediction, electromagnetic simulations, and measurement were found. Experimental results showed stop-band levels higher than −30 dB for compact embroidered metamaterial e-textiles. The validated results confirmed embroidery as a useful technique to obtain customized electromagnetic properties, such as filtering, on wearable applications.

This paper presents an alternative process to fabricate flexible bandpass filters by using an embroidered yarn conductor on an electronic textile. The novelty of the proposed miniaturized filter is its complete integration on the outfit, with benefits in terms of compressibility, stretchability, and high geometrical accuracy opening the way to develop textile filters for wearable applications in sport and medicine. The proposed design consists of a fully embroidered microstrip topology with a length equal to quarter wavelength (λ/4) to develop a bandpass filter frequency response. A drastic reduction in the size of the filter was achieved by taking advantage of a simplified architecture based on meandered-line stepped impedance resonator. The e-textile microstrip filter was designed, simulated, fabricated, and measured with experimental validation at a 7.58 GHz frequency. The insertion loss obtained by simulation of the filter was substantially small. The return loss was greater than 20 dB for bands. To explore the relations between the physical parameters and filter performance characteristics, a theoretical equivalent circuit model of the filter constituent components was studied. The bending effect of the e-textile filter was also studied. The results showed that by raising the radius of bending to 40 mm, the resonance frequency was raised to 4.25 MHz/mm.

In this work, two embroidered textile moisture sensors are presented. The sensors are based on a capacitive interdigitated structure embroidered on a cotton substrate with an embroidery conductor yarn composed by 99% pure silver plated nylon yarn 140/17 dtex. In order to evaluate the sensor sensitivity, the impedance of the sensor has been measured by means of a LCR meter from 20 Hz to 20 kHz on a climatic chamber with a sweep of the relative humidity from 25% to 65% at 20 °C. The experimental results show a clear and controllable dependence of the sensor impedance with the relative humidity. Therefore, this dependence points out the usefulness of the proposed sensor to develop wearable applications on health and fitness scope.

In this work, the utilization of different textile materials for manufacturing of metamaterial with the aim of controlling the signal propagation on smart textile applications is investigated. The performance of composite structures of embroidered yarn conductor transmission lines loaded with split-ring resonator geometries in felt and cotton substrates are reported. The proposed structure allows propagating or filtering the transmitted signal in the microwave frequency range. The experimental results exhibit a rejection band between 1.3 and 2.6 GHz for felt substrate and between 1.6 and 2.6 GHz for cotton substrate with stop-band levels lower than-20 dB. The presented e-textile structures are designed, electromagnetically simulated and measured. The measured results are in good agreement with 3D electromagnetic simulations. The effect of bending of the e-textiles for realistic scenario is also studied. The experimental results show that by changing the radius of bending from 10 mm to 65 mm, the resonance frequency is shifted up 290 MHz and 144 MHz for cotton and felt substrates, respectively.

In this paper a metamaterial wearable antenna is proposed. The proposed design is based on a transmission line coupled to a pair of double ring resonators (DRRs) on an e-textile substrate. The metallic antenna layer is fully embroidered providing both electromagnetic and mechanical good properties. The proposed design is validated by comparison of 3D electromagnetic simulations and measurements. The obtained results correspond to S 11 < À29.5 dB with a gain of 9.64 dBi at resonance frequency and 93% efficiency covering a 160 MHz bandwidth. In addition, the effect of environmental condition such as temperature and humidity on antenna is reported. Results show the resonance frequency level shift in several climatic conditions. Moreover, the specific absorption rate (SAR) to preserve the human body safety from radiation is performed by means of numerical simulations, according to the international regulation. Experimental results confirm that the embroidered MTM antenna is a useful technique to control the propagation of signals on wearable applications.

In this paper, the utilization of common fabrics for the manufacturing of e-textile metamaterial is investigated. The proposed design is based on a transmission line loaded with split-ring resonators (SRRs) on a cotton substrate for filter signal application. The proposed design provides a stop band between 2.7 GHz and 4.7 GHz, considering a four stage SRR topology. Experimental results showed stop band levels higher than −30 dB for the proposed compact embroidered metamaterial e-textiles. The validated results confirmed embroidery as a useful technique to obtain customized electromagnetic filter properties, such as transmitted signal filtering and control, on wearable tech device applications.