Search Results (20)

This paper presents a study on the repeatability of washing effects on two antenna-based sensors for breathing monitoring. One sensor is an embroidered meander antenna-based sensor integrated into a T-shirt, and the other is a loop antenna integrated into a belt. Both sensors were subjected to five washing cycles, and their performance was assessed after each wash. The embroidered meander antenna was specifically compared before and after washing to monitor a male volunteer’s different breathing patterns, that is, eupnea, apnea, hypopnea, and hyperpnea. Stretching tests were also conducted to evaluate the impact of mechanical deformation on sensor behavior. The results highlight the changes in sensor performance across multiple washes and stretching conditions, offering insights into the durability and reliability of these embroidered and loop antennas for practical applications in wearable health monitoring. The findings emphasize the importance of considering both washing and mechanical stress in the design of robust antenna-based sensors. Full article

The production of consumer electronics using electrically conductive materials is a dynamically developing sector of the economy. E-textiles (electronic textiles) are also used in radio frequency identification technology, mainly in the production of tag antennas. For economic reasons, it is important that the finished product is universal, although frequencies in radio systems have different values in different regions of the world. Therefore, the antenna bandwidth must be sufficiently wide so that the read range of the tag is maximally large for all frequencies of the specified band. The bandwidth of an antenna depends on its type and geometric dimensions, but this parameter can also be influenced by the way a given type of antenna is made. The authors prepared samples of embroidered RFID tag antennas for the UHF band using various types of embroidery. Then, its impedance and the read range of the tag were examined in order to determine the exact influence of the type of embroidery on the parameter of interest (antenna bandwidth). The results obtained during the research indicate the influence of different embroidery styles is present; however, that influence is not significant. Full article

A design framework for developing full-textile reconfigurable dipole antennas is proposed for wearable applications. To this end, a precise embroidery process using conductive threads is applied to properly manage the antenna structure. Further, mechanical reconfiguration to enhance antenna operation by using solely clothing components is outlined. As a proof-of-concept, we present a full-textile embroidered dipole antenna with mechanical frequency reconfiguration. Specifically, reconfiguration is achieved by folding the dipole arms through a triangular formation. Conductive Velcro strips are employed to guide the necessary dipole arrangement. As shown, the proposed design methodology enables frequency tunability that ranges from 780 to 1330 MHz for UHF and L bands, with satisfactory radiation performance. The measured and simulated results are in good agreement, in terms of achieving similar frequency reconfiguration concept, as predicted by the electromagnetic simulation models. Full article

A textile bandwidth-enhanced half-mode substrate-integrated cavity (HMSIC) antenna based on embroidered shorting vias is designed. Based on the simulated results of the basic HMSIC antenna, two embroidered hollow posts with square cross-sections are added as shorting vias at the intersections of the zero-E traces of the ${\mathrm{T}\mathrm{M}}_{210}^{\mathrm{H}\mathrm{M}}$ and ${\mathrm{T}\mathrm{M}}_{020}^{\mathrm{H}\mathrm{M}}$ modes to shift the ${\mathrm{T}\mathrm{M}}_{010}^{\mathrm{H}\mathrm{M}}$-mode band to merge with the bands of the higher-order modes for bandwidth enhancement. A prototype is practically fabricated based on computerized embroidery techniques. Measurement results show that the prototype is of an expanded −10 dB impedance band of 4.87~6.17 GHz (23.5% fractional bandwidth), which fully covers the 5 GHz wireless local area network (WLAN) band. The simulated radiation efficiency and maximum gain of the proposed antenna are above 97% and 7.6 dBi, respectively. Furthermore, simulations and measurements prove its robust frequency response characteristic in the proximity of the human tissues or in bending conditions, and the simulations of the specific absorption rate (SAR) prove its electromagnetic safety on the human body. Full article

This article presents an innovative combination of textile electrical circuits with advanced capabilities of electronic RFID sensors, indicating the revolutionary nature of the development of textronics, which is used in various areas of life, from fashion to medicine. A review of the literature relating to the construction of textronic RFID identifiers and capacitive textronic sensors is performed. Various approaches to measuring capacity using RFID tags are discussed. This article focuses on presenting the concept of a capacitive sensor with an RFID interface, consisting of a microelectronic part and a textile part. The textile part is based on the WL4007 material, where antennas and capacitive sensors are embroidered using SPARKFUN DEV 11791 conductive thread. The antenna is a half-wave dipole designed to operate at a frequency of 860 MHZ. The microelectronic part is sewn to the textile part and consists of a microcontroller, an RFID-integrated circuit and a coupling loop, placed on the PCB. The embroidered antenna is coupled with a loop on the microelectronic module. This article focuses on presenting various designs of textronic electrodes, enabling various types of measurements. Article presents capacitance measurements of individual sensor electrodes, made using a measuring bridge and a built RFID tag. The sensors’ capacity measurement results are shown. Full article

The aim of this paper is to demonstrate progress in textronic UHF RFID transponder (RFIDtex tag) technology. The fundamental idea behind the RFIDtex tag design involves galvanic separation between circuits of the sewn antenna and the chip, which are electromagnetically coupled through a system of inductive loops. To advance the development of this concept, it is crucial to detect factors affecting the performance of the transponders. To achieve this goal, a mathematical model of the textronic UHF RFID transponder was developed. It involves relationships that describe the impedance of each element, the mutual inductance of the loops, and the chip voltage, and it enables the exploration of the influence of these variables on general parameters such as impedance matching and read range. Various analytical and numerical approaches were considered to obtain the value of the mutual inductance of the loops. The dimensions and geometry of the antenna, as well as the matching circuit in the microelectronic module, were taken into account. Based on the mathematical model, it was determined that mutual inductance strongly affects the chip voltage for frequencies higher than 800 MHz. The calculations from the mathematical model were compared with numerical simulations. Experimental studies were also conducted to investigate how the transponder performance is affected by either the distance between the centers of the loops or the conductivity of the threads used to embroider the antenna. The measurement results allowed us to conclude that even small imperfections in the manufacturing of the transponder, which slightly increase the vertical or horizontal distance between the centers of the loops, cause a dramatic decrease in the mutual inductance and coupling coefficient, significantly impacting the transponder’s performance. Full article

The idea of novel antennas and matching circuits, developed for radio frequency identification (RFID) passive transponders, and made on textile substrates, is presented in this paper. By manufacturing an RFID transponder by the means used in every clothing factory, we developed the concept of RFIDtex tags, which, as textronic devices, make a new significant contribution to the Internet of Textile Things (IoTT). The main feature of the device consists of the use of an uncommon inductively coupled system as the antenna feed element. The antenna is sewn/embroidered with a conductive thread, and the microelectronic module with an RFID chip is made in the form of a bead, using standard electronic technology. Finally, the construction of the RFIDtex tag is developed for easy implementation in production lines in the garment industry. The proposed inductive coupling scheme has not been considered anywhere, so far. The developed transponder is dedicated to operating in RFID systems of the ultra-high frequency band (UHF). The numerical calculations confirmed by the experimental results clearly indicate that the proposed coupling system between the antenna and the microelectronic module works properly and the RFIDtex device can operate correctly within a distance of several meters. The proposed design is based on the authors’ patent on the textronic RFID transponder (patent no PL 231291 B1). Full article

Wearable technology has been getting more attention for monitoring vital signs in various medical fields, particularly in breathing monitoring. To monitor respiratory patterns, there is a current set of challenges related to the lack of user comfort, reliability, and rigidity of the systems, as well as challenges related to processing data. Therefore, the need to develop user-friendly and reliable wireless approaches to address these problems is required. In this paper, a novel, full, compact textile breathing sensor is investigated. Specifically, an embroidered meander dipole antenna sensor integrated into an e-textile T-shirt with a Bluetooth transmitter for real-time breathing monitoring was developed and tested. The proposed antenna-based sensor is designed to transmit data over wireless communication networks at 2.4 GHz and is made of a silver-coated nylon thread. The sensing mechanism of the proposed system is based on the detection of a received signal strength indicator (RSSI) transmitted wirelessly by the antenna-based sensor, which is found to be sensitive to stretch. The respiratory system is placed on the middle of the human chest; the area of the proposed system is 4.5 × 0.48 cm², with 2.36 × 3.17 cm² covered by the transmitter module. The respiratory signal is extracted from the variation of the RSSI signal emitted at 2.4 GHz from the detuned embroidered antenna-based sensor embedded into a commercial T-shirt and detected using a laptop. The experimental results demonstrated that breathing signals can be acquired wirelessly by the RSSI via Bluetooth. The RSSI range change was from −80 dBm to −72 dBm, −88 dBm to −79 dBm and −85 dBm to −80 dBm during inspiration and expiration for normal breathing, speaking and movement, respectively. We tested the feasibility assessment for breathing monitoring and we demonstrated experimentally that the standard wireless networks, which measure the RSSI signal via standard Bluetooth protocol, can be used to detect human respiratory status and patterns in real time. Full article

A textile, embroidered antenna, based on the fractal shape of the Sierpinski triangle, is designed in this paper for operation in the European free Industrial Scientific and Medical (ISM) 863–870 MHz band, as well as in the 902–928 MHz band designated for ISM applications in North and South America. Several prototypes have been fabricated by employing different stitch patterns and thread materials. The effect of the fabrication parameters on the performance of the proposed antenna is investigated through measurements and simulations, with the results being in good agreement. The antenna exhibits attractive characteristics such as wide bandwidth, relatively stable radiation patterns, as well as robustness in washing. Several tests reveal that convex and concave bent conditions do not affect the coverage of the aforementioned ISM bands, despite the shift of the resonant frequency in some cases. Moreover, the SAR values resulting from simulations are below the corresponding thresholds suggested by international guidelines. Full article

In this paper, a feasibility study of a microwave antenna-based sensor is proposed for in vitro experiments for monitoring blood glucose levels. The proposed device consists of a square-ring incorporated within a fully textile monopole antenna to absorb and sense different glucose concentrations, covering patients with different diabetic conditions. The designed antenna-sensor is optimized to operate at 2.4 GHz. The sensing principle is based on the resonance frequency shift of the reflection response of the antenna-based sensor under different glucose levels. The experiments were carried out with blood mimicking by means of aqueous solutions, using D(+)- glucose/water in different concentrations for various diabetic conditions of type-2 diabetes. The performance of the embroidered antenna-based sensor is characterized and validated using a convenient setup for in vitro measurements. The results demonstrated the ability of the proposed antenna-based sensor to cover all the glucose levels of the diabetes range, including hypoglycemia (10–70 mg/dL), normoglycemia (80–110 mg/dL) and hyperglycemia (130–190 mg/dL) with a sensitivity of 350 kHz/(mg/dL). Besides its ability to detect different glucose concentrations of various diabetic conditions, the proposed antenna-sensor presents diverse features such as a simplistic design, compact size, wearability and low cost. The proposed textile device demonstrates a proof of concept for efficient in vitro blood glucose level measurements and diagnostics of diabetes. Full article

Moisture causes detuning and increased losses in textile antennas, and it affects resonant and wideband textile antennas differently. In this work, we studied the effect of moisture on a resonant textile planar inverted-F antenna (PIFA) and a wideband textile monopole antenna. Both antennas were manufactured by embroidering conductive yarn in denim textile. The input reflection coefficient, antenna gain, and gain patterns were measured on both antennas for different moisture contents. The results show that wideband antennas are less affected by moisture in comparison with resonant antennas. For communications applications, large moisture content in the textile antenna should be avoided; therefore a flexible, textile-based waterproofing antenna cover was proposed, manufactured, and tested. On the other hand, the effect of antenna detuning by moisture can be used for moisture-sensing application. This concept was demonstrated on the resonant textile PIFA in transmission and reflection setups, showing that the reflection setup gives better results. Full article

Radio frequency energy harvesting (RFEH) and wireless power transfer (WPT) are increasingly seen as a method of enabling sustainable computing, as opposed to mechanical or solar EH WPT does not require special materials or resonators and can be implemented using low-cost conductors and standard semiconductor devices. This work revisits the simplest antenna design, the wire monopole to demonstrate the lowest-footprint, lowest-cost rectifying antenna (rectenna) based on a single Schottky diode. The antenna is fabricated using a single Litz-wire silk-coated thread, embroidered into a standard textile substrate. The rectifier is fabricated on a compact low-cost flexible printed circuit board (PCB) using ultra-thin polyimide copper laminates to accommodate low-footprint surface mount components. The antenna maintains its bandwidth across the 868/915 MHz license-free band on- and off-body with only −4.7 dB degradation in total efficiency in human proximity. The rectenna achieves up to 55% RF to DC efficiency with 1.8 V DC output, at 1 mW of RF power, demonstrating its suitability as a power-supply unit for ultra-low power e-textile nodes. Full article

This paper deals with the design and fabrication of durable radio frequency identification (RFID) passive tag with inductive coupling, operating at ultra-high frequencies, dedicated to the identification and monitoring of professional textile products. A reliable architecture for the tag transponder is proposed, featuring a minimal number of galvanic contacts: The two pins of the integrated circuit are connected to the terminals of the inductive coupling loop by using surface mount technology welding. The transponder is encapsulated with an electrically insulating material which is waterproof and resistant to mechanical, thermal, and chemical stress. The antenna is inductively coupled to the transponder through a double loop which substantially reduces the length of the tag and significantly improves the coupling factor, enabling the tag to operate at a low power level. The reliability and flexibility of the tag is obtained by using appropriate materials and manufacturing methods for the ultra-high frequency (UHF) antenna by embroidering a multifilament stainless steel wire on textile support. The washing cycle tests have validated the applicability of this flexible and washable RFID tag, and its electromagnetic performance was experimentally assessed in an independent laboratory. Full article

Achieving a wireless power transfer (WPT) link insensitive to separation is a key challenge to achieving power autonomy through wireless-powering and wireless energy harvesting over a longer range. While coupled WPT has been widely used for near-field high-efficiency WPT applications, the efficiency of the WPT link is highly sensitive to separation and alignment, making it unsuitable for mobile systems with unknown or loose coupling such as wearables. On the other hand, while ultra-high frequency (UHF) and microwave uncoupled radiative WPT (0.3–3 GHz) enables meters-long separation between the transmitter and the receivers, the end-to-end efficiency of the WPT link is adversely limited by the propagation losses. This work proposes radiative WPT, in the 6.78 MHz license-free band, as a hybrid solution to separation-independent WPT, thus mitigating the losses associated with coil separation. Resonant electrically small antennas were fabricated using embroidered textile coils and tuned using L-matching networks, for wearable WPT. The antenna’s efficiency and near-fields have been evaluated numerically and experimentally. The proposed WPT link achieves a stable forward transmission of S ${}_{21}>-17$ dB and S ${}_{21}>-$ 28 dB, independent of coil separation on the XZ and XY planes respectively, in a 27 m ${}^3$ volume space. The presented approach demonstrates the highest WPT link efficiency at more than 1-m separation and promises higher end-to-end efficiency compared to UHF WPT. Full article

A flexible and totally wearable textile antenna is proposed by embroidering the conductive threads into garments. A purely polyester substrate has been utilized, which provides a tag that can be easily integrated with the clothes. The proposed tag antenna is small with dimensions of 72 × 20 × 2.75 mm³ and offers an enhanced performance in terms of gain and stability when worn on different body locations. Experimental results demonstrate an improved impedance matching owing to the elasticity of the E-shaped inductive feeder. Close agreement has been achieved between the simulated and measured results. Full article