Textile UHF-RFID antenna sensors based on material features, interfaces and application scenarios

Tesi en modalitat de compendi de publicacions, amb una secció retallada per drets de l'editor. In reference to IEEE copyrighted material which is used with permission in this thesis, the IEEE does not endorse any of Universitat Politècnica de Catalunya's products or services. Internal or personal use of this material is permitted. If interested in reprinting/republishing IEEE copyrighted material for advertising or promotional purposes or for creating new collective works for resale or redistribution, please go to http://www.ieee.org/publications_standards/publications/rights/rights_link.html to learn how to obtain a License from RightsLink.Radio frequency identification over measurable ultra-high frequency textile substrates (UHF-RFID) is a promising technology to develop new applications in the field of health and the Internet of Things (IOT), due to the massive use of fabrics and the technological maturity of embroidery techniques. This thesis is the result of a compendium of publications on this topic. First, as a result of the analysis of the state of art, a systematic review entitled 'Wearable textile UHF-RFID sensors: A systematic review' has been published. The thesis aims to improve research on UHF-RFID textile-based sensor technology. Thanks to the analysis of the state of art, three novel research objectives have been set that are worth exploring. The first is to study novel detection functions for textile UHF-RFID based sensor technology; the second is to find a connection/interface solution between textile antennas and integrated circuit (IC) chips and the third is to reduce the costs of such technology to promote future commercial applications. To contextualize the thesis, it includes the necessary theoretical fundamentals and the manufacturing and characterization methods used during it. As a result of the work derived from the first objective, a scientific article entitled “Textile UHF-RFID Antenna Sensor for Measurements of Sucrose Solutions in Different Levels of Concentration” has been published. In this work, a textile UHF-RFID tag with two detection positions is proposed for sucrose solution measurements. The two detection positions with the different detection functions show good performance and can offer two options for future full applications. In addition, another scientific article entitled “ Textile UHF-RFID Antenna Embroidered on Surgical Masks for Future Textile Sensing Applications” has been published to support the first objective. The inspiration for this work came from the current pandemic situation. This work develops three progressive designs of textile UHF-RFID antennas over surgical masks due to the current global epidemic situation. Reliability testing demonstrated that the proposed designs can be used for human healthcare focused applications. As a result of the second objective, a research article entitled 'Experimental Comparison of Three Electro-textile Interfaces for Textile UHF-RFID Tags on Clothes' has been published. This work proposes three electro-textile interfaces integrated with the corresponding textile UHF-RFID antennas and provides the chip-textile connection solutions (through sewing, push buttons and insertion). As a result of this objective, an electro-textile interconnect system has been proposed together with its electrical model, which allows the correct adaptation of impedances between the RFID antennas and the integrated circuit. It is worth noting that the mixed-use feasibility of the proposed electro-textile interfaces and the designed textile UHF-RFID antennas has been verified, reducing the cost in the design procedure in applications where the read range requirements of the order of 1 meter. The third objective has been achieved and exposed by a scientific article entitled 'Electro-textile UHF-RFID Compression Sensor for Health-caring Applications'. It proposes a single UHF-RFID based compression textile sensor that can be used simultaneously in two different healthcare application scenarios, which directly impacts on cost reduction.La identificación por radiofrecuencia sobre substratos textiles de ultra alta frecuencia (UHF-RFID) con capacidad de medida es una tecnología prometedora para desarrollar nuevas aplicaciones en el campo de la salud y el Internet de las cosas (IOT), debido a la masiva utilización de los tejidos y a la madurez tecnológica de las técnicas de bordado. Esta tesis es el resultado de un compendio de publicaciones sobre dicha temática. En primer lugar, como resultado del análisis del estado del arte se ha publicado una revisión sistemática titulada 'Wearable textile UHF-RFID sensors: A systematic review'. La tesis tiene como objetivo mejorar la investigación sobre la tecnología de sensores basada en textiles UHF-RFID. Gracias al análisis del estado del arte se han fijado tres objetivos de investigación novedosos que vale la pena explorar. El primero es estudiar funciones de detección novedosas para la tecnología de sensores basada en UHF-RFID textiles; el segundo es encontrar una solución de conexión/interfaz entre antenas textiles y chips de circuito integrado (IC) y el tercero es la reducción de costes de dicha tecnología para promover futuras aplicaciones comerciales. Para contextualizar la tesis, ésta incluye los fundamentos teóricos necesarios y los métodos de fabricación y caracterización utilizados durante la misma. Como resultado del trabajo derivado del primer objetivo, se ha publicado un artículo científico titulado “Textile UHF-RFID Antenna Sensor for Measurements of Sucrose Solutions in Different Levels of Concentration”. En este trabajo, se propone una etiqueta UHF-RFID textil con dos posiciones de detección para mediciones de solución de sacarosa. Las dos posiciones de detección con las diferentes funciones de detección muestran un buen rendimiento y pueden ofrecer dos opciones para futuras aplicaciones completas. Además, se ha publicado otro artículo científico titulado "Textile UHF-RFID Antenna Embroidered on Surgical Masks for Future Textile Sensing Applications" para respaldar el primer objetivo. La inspiración para este trabajo vino de la actual situación de pandemia. En este trabajo se desarrollan tres diseños progresivos de antenas UHF-RFID textiles sobre mascarillas quirúrgicas debido a la situación epidémica mundial actual. Las pruebas de fiabilidad demostraron que los diseños propuestos se pueden usar para aplicaciones centradas en el cuidado de las personas. Como resultado del segundo objetivo, se ha publicado un artículo de investigación titulado 'Experimental Comparison of Three Electro-textile Interfaces for Textile UHF-RFID Tags on Clothes'. En este trabajo se proponen tres interfaces electro-textiles integradas con las correspondientes antenas UHF-RFID textiles y se aportan las soluciones de conexión chip-textil (mediante costura, botones a presión e inserción). Como resultado de este objetivo, se ha propuesto un sistema de interconexión electro-textil junto con su modelo eléctrico, lo que permite la correcta adaptación de impedancias entre las antenas RFID y el circuito integrado. Vale la pena señalar que se ha verificado la viabilidad de uso mixto de las interfaces electro-textiles propuestas y las antenas UHF-RFID textiles diseñadas, lo que reduce el coste en el procedimiento de diseño en aplicaciones donde los requerimientos de rango de lectura del orden de 1 metro. El tercer objetivo se ha alcanzado y expuesto mediante un artículo científico titulado 'Electro-textile UHF-RFID Compression Sensor for Health-caring Applications'. En él, se propone un único sensor textil de compresión basado en UHF-RFID que puede ser utilizado a la vez en dosPostprint (published version

An embroidered passive textile RFID tag based on a T-matched antenna

This paper addresses the design and fabrication of an embroidered textile RFID tag antenna. The main feature of this design is that we have embroidered an RFID chip on the textile support which avoids the use of metallic wires or soldering. The modeled equivalent circuit of the tag is presented to get physical insight into RFID tag antenna design. The detailed results given in this paper include the effect of the bending and the human body proximity on the antenna performance. It is shown that the bending does not introduce a conspicuous effect on the tags read range while the dissipative characteristics of the human body cause a gain and read range reduction. The proposed design may find applications in wearable devices dedicated to health monitoring applications.Peer ReviewedPostprint (author's final draft

Manufacturing And Evaluation Of Stretchable Embroidered Passive Rfid Tags On 3d-printed Substrates

Stretchable electronics is an emerging field of electronics where the devices produced can undergo several mechanical stress conditions but maintain its structural integrity and electrical performance. Categorized under flexible electronics, it is still emerging as a new field of study where the flexible products produced are subjected to extreme mechanical conditions, like stretch and other mechanically induced stresses. It is envisioned that flexible and stretchable electronics will replace the traditional solid-state electronics that we are accustomed to in our everyday lives. The challenges that lie ahead of flexible and stretchable electronics is the research and development of new materials that adhere to its requirements. Some new materials have already been developed and have been used commercially in a limited capacity, especially in the field of biomedical technology. Development of new materials, which usually involve adjustment of the physical and chemical properties of known materials to achieve the requirements of flexibility and stretch abilities, has been a challenging process. This thesis is a study of one such material, known as NinjaFlex, a flexible material used for 3D printing, and is used for manufacturing products which are flexible. Using Fused Deposition Modelling (FDM) printing methods, flexible substrates were produced, upon which an antenna pattern was embroidered using conductive thread, and then a tag IC was attached on the matching part using conductive glue, hence developing passive Ultra High Frequency (UHF) Radio Frequency Identification (RFID) tags with different structural properties for observing their read ranges under stretch conditions. Despite the challenges encountered during the development process, the tags performed well within the desired parameters. The tags responded to the reader’s signal at optimal ranges. The tags, whose original length is of 14 cm each, responded to the reader at acceptable read ranges despite being subjected to stress causing its length to change by 2 cm. Further improvements in the testing processes could be achieved if the tags are produced in a more automated process, and avoidance of signal affecting factors that resulted in the outcomes in this thesis

Clothing-Integrated Human-Technology Interaction

Due to the different disabilities of people and versatile use environments, the current handheld and screen-based digital devices on the market are not suitable for all consumers and all situations. Thus, there is an urgent need for human- technology interaction solutions, where the required input actions to digital devices are simple, easy to establish, and instinctive, allowing the whole society to effortlessly interact with the surrounding technology. In passive ultra-high frequency (UHF) radio frequency identification (RFID) systems, the tag consists only of an antenna and a simple integrated circuit (IC). The tag gets all the needed power from the RFID reader and can be thus seamlessly and in a maintenance-free way integrated into clothing. In this thesis, it is presented that by integrating passive UHF RFID technology into clothing, body movements and gestures can be monitored by monitoring the individual IDs and backscattered signals of the tags. Electro-textiles and embroidery with conductive thread are found to be suitable options when manufacturing and materials for such garments are considered. This thesis establishes several RFID- based interface solutions, multiple types of inputs through RFID platforms, and controlling the surrounding and communicating with RFID-based on/off functions. The developed intelligent clothing is visioned to provide versatile applications for assistive technology, for entertainment, and ambient assistant living, and for comfort and safety in work environments, just to name a few examples

Dense and long-term monitoring of Earth surface processes with passive RFID -- a review

Billions of Radio-Frequency Identification (RFID) passive tags are produced yearly to identify goods remotely. New research and business applications are continuously arising, including recently localization and sensing to monitor earth surface processes. Indeed, passive tags can cost 10 to 100 times less than wireless sensors networks and require little maintenance, facilitating years-long monitoring with ten's to thousands of tags. This study reviews the existing and potential applications of RFID in geosciences. The most mature application today is the study of coarse sediment transport in rivers or coastal environments, using tags placed into pebbles. More recently, tag localization was used to monitor landslide displacement, with a centimetric accuracy. Sensing tags were used to detect a displacement threshold on unstable rocks, to monitor the soil moisture or temperature, and to monitor the snowpack temperature and snow water equivalent. RFID sensors, available today, could monitor other parameters, such as the vibration of structures, the tilt of unstable boulders, the strain of a material, or the salinity of water. Key challenges for using RFID monitoring more broadly in geosciences include the use of ground and aerial vehicles to collect data or localize tags, the increase in reading range and duration, the ability to use tags placed under ground, snow, water or vegetation, and the optimization of economical and environmental cost. As a pattern, passive RFID could fill a gap between wireless sensor networks and manual measurements, to collect data efficiently over large areas, during several years, at high spatial density and moderate cost.Comment: Invited paper for Earth Science Reviews. 50 pages without references. 31 figures. 8 table

Textile materials

In this specialised publication, the reader will find research results and real engineering developments in the field of modern technical textiles. Modern technical textile materials, ranging from ordinary reinforcing fabrics in the construction and production of modern composite materials to specialised textile materials in the composition of electronics, sensors and other intelligent devices, play an important role in many areas of human technical activity. The use of specialized textiles, for example, in medicine makes it possible to achieve important results in diagnostics, prosthetics, surgical practice and the practice of using specialized fabrics at the health recovery stage. The use of reinforcing fabrics in construction can significantly improve the mechanical properties of concrete and various plaster mixtures, which increases the reliability and durability of various structures and buildings in general. In mechanical engineering, the use of composite materials reinforced with special textiles can simultaneously reduce weight and improve the mechanical properties of machine parts. Fabric- reinforced composites occupy a significant place in the automotive industry, aerospace engineering, and shipbuilding. Here, the mechanical reliability and thermal resistance of the body material of the product, along with its low weight, are very relevant. The presented edition will be useful and interesting for engineers and researchers whose activities are related to the design, production and application of various technical textile materials

Advances in Antennas and High-Frequency Material Characterization for Wireless Body-Area Networks

The development of the personal body-centric communication system is an essential part of the novel generation of wireless communication systems and one of the communication technology challenges. The versatility of body-centric communication revolutionizes healthcare by allowing continuous and in-all- conditions human health monitoring and human-centered authentication. Recently, with the extra-low power consumption and low-complexity backscatter communications, the passive ultra-high-frequency (UHF) radio-frequency identification (RFID) technology has been considered a promising approach for the wireless body area network. An inevitable part of this system is the wearable antenna, which plays a critical role in ensuring the efficient wireless link of the signal in the presence of the wearer. The wearable antenna should be fabricated with textile materials and equipped with various radiation configurations to enhance robustness and the operation’s versatility for long-term use. The difficulty of the wearable antenna development is to obtain the property information of the unknown textile substrate and conductor. To address the above-mentioned challenges, this thesis starts with the novel textile material characterization method to single out the relative permittivity and loss tangent of the substrate and bulk conductivity of the conductor. Unlike conventional approaches, our method simply applied the testing structure of the microstrip line composed of the textile material and simple data processing with the least square estimation. Then, a variation of the textile wearable antenna development with a low-profile planar in geometry is proposed in the next part of the thesis. The headgear RFID tag and forearm RFID reader antennas were developed based on quasi-Yagi configurations and periodic surface to obtain a directive pattern along the body surface. Another type of antenna configuration developed in this thesis is the circular polarization patch antenna for the wearable RFID tag. This type of antenna significantly reduced the polarization mismatch between the reader and the tag; hence, the detection capability and radiation efficiency are remarkably upgraded. The promising performance of the antennas was rigorously analyzed in simulation and verified with on-body measurement

Coupled eighth-mode substrate integrated waveguide antenna: small and wideband with high-body antenna isolation

A novel antenna design for wideband operation is presented, consisting of a system of two coupled miniaturized eighth-mode resonant radiating cavities with a low-complexity feeding network. The design methodology relies on the virtual magnetic boundaries along the symmetry planes of a rectangular waveguide resonator, for size reduction, and the frequency bifurcation of two tightly coupled resonators, for bandwidth enhancement. After discussing its operating principle, a prototype targeting wearable applications is designed, manufactured, and validated. Multiband operation is achieved with simultaneous coverage of the 2.4-GHz ISM band and the LTE-7 up- and downlink-bands. Measurements in free-space and on-body scenarios validate the antenna's performance. A bandwidth of 414 MHz (16.2%) is measured, as well as a maximal gain of 4.7 dBi. The directive patch-like radiation pattern and the ground plane topology lead to high body-antenna isolation and good on-body performance. Impedance bandwidth and radiation pattern remain stable when the antenna is worn by a person and bent around a cylinder to mimic deformation

Graphene-based soft wearable antennas

Electronic textiles (e-textiles) are about to face tremendous environmental and resource challenges due to the complexity of sorting, the risk to supplies and metal contamination in textile recycling streams. This is because e-textiles are heavily based on the integration of valuable metals, including gold, silver and copper. In the context of exploring sustainable materials in e-textiles, we tested the boundaries of chemical vapour deposition (CVD) grown multi-layer (ML) graphene in wearable communication applications, in which metal assemblies are leading the way in wearable communication. This study attempts to create a soft, textile-based communication interface that does not disrupt tactile comfort and conformity by introducing ML graphene sheets. The antenna design proposed is based on a multidisciplinary approach that merges electromagnetic engineering and material science and integrates graphene, a long-lasting alternative to metal components. The designed antenna covers a wide bandwidth ranging from 3 GHz to 9 GHz, which is a promising solution for a high data rate and efficient communication link. We also described the effects of bending and proximity to the human body on the antenna's overall performance. Overall, the results suggested that graphene-based soft antennas are a viable solution for a fully integrated textile-based communication interface that can replace the current rigid, restrictive and toxic approaches, leading to a future where eco-friendliness and sustainability is the only way forward