Bahareh Moradi

This paper presents a contact bracelet-type microwave sensor, implemented on fabric, able to monitor the wrist pulse wave (WPW) and, consequently, the heart rate of the individual under analysis. The device operates in transmission, and the working principle is the variation of the frequency response as consequence of pressure changes exerted on a diaphragm caused by blood pumping in the radial artery. The associated electronics to implement a stand-alone device (avoiding the use of a vector network analyzer) are also included. Specifically, by using a phase or an envelope detector, the system provides either the phase or the magnitude of the output signal at a specific frequency, namely, the WPW. The main relevant contribution of the paper is the implementation and validation of the sensor in a textile (and hence flexible and conformal) substrate, using also textile conductors. By this means, the device features a low cost, profile, and weight, making it ergonomic and user-friendly for real usage. Comparison of the recorded signal of the sensor on multiple individuals (at rest, under motion, and by wetting their wrist skin) with Photoplethysmography (PPG) further validates the approach.

This paper proposes a system for monitoring respiration wirelessly. The system is composed of a stretchable belt that should be placed in the thorax or abdomen of the individual under analysis, a textile microwave sensor integrated on it, and the associated electronics for signal generation, processing, and communication. The sensing module detects the breath rate through the variation in the phase of the reflection coefficient of a transmission line loaded with a movable resonator, caused by the elongation and contraction of the belt. Both elements, the line and the resonator (an electric-LC −ELC− resonator), are implemented in cotton substrate with metallic layers (including the ground plane, the microstrip line, and the ELC resonator) consisting of a conductive textile material tapered to the substrate. Advantageously, the sensor operates at a single frequency, resulting in simple associated electronics, essentially, a voltage-controlled oscillator (VCO), a phase detector, and a power splitter (implemented by means of a directional coupler), necessary to generate a reference signal for the phase detector. Additionally, the system incorporates a microcontroller that manages the VCO, captures the phase of the detector, and transmits it to the receiver (a smartphone) via Bluetooth. The functionality of the system is demonstrated by using it in a volunteer breathing under different conditions.

This work focuses on the early detection of urine leakage. We present a novel embroidered textile microwave sensor for real-time leakage detection. The proposed sensor is implemented in a woven textile substrate (cotton), with the sensing element embroidered using silver-plated conductive yarn and the ground plane realized with a homogeneous conductive textile. The sensor is a two-port structure consisting of a 50-Ω matched line loaded with an open-ended stub resonator, the sensitive element, and the transduction mechanism is the change in the electrical length of such stub resonator caused by urine dropping or pouring. The sensor is tolerant to mechanical stress, evaluated by bending it, and it can discriminate 50 μL droplets of urine. It has been found that by considering the magnitude of the transmission coefficient at 2.4 GHz (the resonance frequency of the bare stub resonator) as output variable, the device can distinguish urine volumes below and above 100 μL, the considered onset of early leakage, by setting the trigger threshold to −11.0 dB. This fully textile-based configuration ensures complete flexibility, enhanced mechanical robustness under deformation, and compatibility with washing processes, essential features for wearable healthcare 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.

In this paper, the utilization of high dielectric constant resonator as a passive element for design of filter in the range of Ku band is investigated. The design is based on a new kind of dielectric resonator fabricated with a commercial high dielectric constant EPOXY paste. The design is based on a microstrip line periodically loaded with a new kind of dielectric resonator fabricated with a commercial high dielectric constant Epoxy paste compatible with serigraphy and screen printing technology.

A novel wearable dipole antenna at 325 MHz resonance frequency is presented in this article. A felt fabric with permittivity 1.2 and thickness 0.7 mm is used as a substrate. The proposed design is validated by comparison of 3D electromagnetic simulations and measurements. The obtained results correspond to S₁₁ < −18 dB and a gain 1.5 dB at resonance frequency, with 49% efficiency and a 20 MHz bandwidth. Moreover, the effect of bending of the e-textiles under realistic scenarios is also studied. The measured results show that by changing the radius of bending from 32.5 to 3 cm, the resonance frequency is shifted up 10 MHz with a sensitivity of 0.285 MHz/cm.

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.

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.

This paper presents an alternative process to fabricate flexible bandpass filters by using embroidered yarn conductor on electronic-textile. The novelty of the proposed miniaturized filter is its complete integration on the outfit, with benefits in terms of compressibility, stretch ability and high geometrical accuracy, opening the way to develop textile filters in sport and medicine wearable applications. 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 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 has been designed, simulated, fabricated and measured, with experimental validation at a 7.58 GHz frequency. The insertion loss obtained by simulation of the filter is substantially small. The return loss is greater than 20 dB for bands. To explore the relations between physical parameters and filter performance characteristics, theoretical equivalent circuit model of the filter constituent components were studied. The effect of bending of the e-textile filter is also studied. The results show that by changing the radius of bending up to 40 mm, the resonance frequency is shifted up 4.25 MHz/mm.