Unobtrusive Implementation of Wireless Electronics into Clothing

Research in flexible and stretchable electronics (FSE) has gained significant momentum in recent years due to being mechanically durable without compromising electrical performance. Newer materials and manufacturing methods are studied for efficiently developing FSEs. These materials and methods can be applied to the widespread development of wearable electronics, particularly clothing-integrated electronics. However, seamlessly integrating clothing into electronics has been quite challenging, where achieving an optimal balance between electrical performance and mechanical reliability is a key issue. This thesis aims to find innovative and novel solutions for integrating electronics into clothing, which could be mechanically durable, with limited compromise to their electrical functionality. This thesis combines 3D printing with passive radio frequency identification (RFID) technology to develop wireless platforms integrated into clothing. 3D printing was used to create encapsulants in which electronic components and antennas, designed with conductive yarns and textiles, were embedded. The wireless platforms developed in this study were tested for their mechanical reliability and evaluated for their wireless performance. This study then extended to RFID sensor development, where stimuli responsive materials were 3D printed onto textiles, and wireless performance concerning stimuli response were observed. This study observed that 3D printing encapsulated RFID-based wireless platforms functioned well regarding their wireless performance, despite exposure to moisture and mechanical stress. Although in their preliminary stages, the sensor platforms were also optimally responsive to moisture and temperature changes. Future studies include further evaluating the 3D printing parameters and materials for better mechanical reliability and more extensive studies on the sensor platforms. The wireless platforms developed in this study can be further developed for applications related to health care, logistics, security, and sensing applications

The Design, Fabrication and Practical Evaluation of Body-centric Passive RFID Platforms

Passive ultra-high-frequency (UHF) radio-frequency identification (RFID) technology is increasingly being recognized as a compelling approach to utilizing energy- and costefficient wireless platforms for a wireless body area network (WBAN). The development of WBANs has stimulated a lot of research over recent years, as they can offer remarkable benefits for the healthcare and welfare sectors, as well as having innovative sportsrelated applications.This thesis is to evaluate and develop the RFID tags used in an integrated wearable RFID platform working in a realistic environment. Each of the wearable antennas were specifically designed for a target part of the body, such as the back or the hand. The antennas were manufactured in different ways, using copper tape, electro-textiles (Etextile) and embroidered conductive threads. After they had been produced, the tags were subjected to on-body measurement and reliability tests. The reliability tests were performed under tough conditions in which the tags were stretched, for instance, or exposed to high humidity and washing. Our results show that the tags can perform well when worn on-body in a harsh environment.This thesis provides several integrated solutions for wireless wearable devices. By different RFID antenna design and fabrication methods, the RFID tag can be used as the moisture and strain sensor with lightweight, small size, flexible pattern and great dailyuse reliability

Characterization and Design Methodologies for Wearable Passive UHF RFID Tag Antennas for Wireless Body-Centric Systems

Radio Frequency Identification (RFID) is a wireless automatic identification technology that utilizes electrically active tags – low-cost and low-power wireless communication devices that let themselves transparently and unobstructively be embedded into everyday objects to remotely track information of the object’s physical location, origin, and ownership. At ultra-high frequencies (UHF), this technology uses propagating electromagnetic waves for communication, which enables the fast identification of tags at large distances. A passive RFID tag includes two main components; a tag antenna and an RFID integrate circuit (tag IC). A passive tag relies solely on the external power harvested from an incident electromagnetic wave to run its circuitry and for data transmission. The passiveness makes the tag maintenance-free, simple, and low-cost, allowing large-scale commercial applications in the supply chain, ticketing, and asset tracking. The future of RFID, however, lies in the transition from traditional embedded applications to wearable intelligent systems, in which the tags are seamlessly integrated with everyday clothing. Augmented with various ambient and biochemical sensors, the tag is capable of detecting physical parameters of its environment and providing continuous monitoring of human vital signs. Tremendous amount of tagged entities establish an intelligent infrastructure that is personalized and tailored to the needs of each individual and ultimately, it recedes into the background of our daily life. Although wearable tags in intelligent systems have the enormous potential to revolutionize the quality of human life, the emerging wearable RFID applications introduce new challenges for designers developing efficient and sophisticated RFID systems. Traditional tag design parameters and solutions will no longer respond to the new requirements. Instead, the whole RF community must adopt new methods and unconventional approaches to achieve advanced wearable tags that are highly transparently integrated into our daily life. In this research work, an empirical as well as a theoretical approach is taken to address the above-mentioned wearable RFID tag challenges. Exploiting new analysis tools in combination with computational electromagnetics, a novel technique to model the human body in UHF applications for initiating the design of optimized wearable tags is developed. Further, fundamental unprecedented UHF characteristics of advanced wearable electronics materials – electro-textiles, are established. As an extremely important outcome of this research work, innovative optimization methodologies for the promotion of novel and advanced wearable UHF antennas are proposed. Particularly, it is evidenced that proper embroidery fabrication techniques have the great potential to realize wearable tag antennas exhibiting excellent RF performance and structural properties for the seamless integration with clothing. The kernel of this research work is the realization of a flexible and fully embroidered passive UHF RFID patch tag prototype achieving optimized performance in close vicinity of the high-permittivity and dissipative human body. Its performance may be considered as a benchmark for future wearable antenna designs. This shows that this research work outcome forms an important contribution to the state of the art and a milestone in the development towards wearable intelligence

Performance evaluation of textile based passive RFID antennas as wearable sensors

Conformal and stretchable wearable sensors provide real-time information about individual's health conditions. There are a lot of vital signs and parameters of the human body that are supposed to be sensed by the sensors like, body movement, body temperature, Electrocardiogram (ECG), Electroencephalogram (EEG) etc. Hence, there are a lot of health tracking devices available in the market for different purposes. One of the most important sensors are the hydration/moisture/humidity sensors. These sensors are required for the health fitness and for the medical care of the patients. However, as far as the skin sensors are concerned, they are facing one important challenge, which is to have better contact with the body to have better results to analyze as well as providing ease and comfort to the patient/user. In this work, Radio frequency identification technology (RFID) has been used to achieve and overcome the challenge. Since RFID is a prevailing technology in which a microchip in a label used to transmit data when the label is exposed to radio waves. RFID technology can easily be understood by the concept of student cards used in our university where student cards are working as the Tag and the readers planted on the door slots read them. The data/information read by the reader is stored in the database for every specific tag (transponder), to be accessed it later. Passive Ultra-High Frequency (UHF) RFID tags are here used as moisture sensors. The tags for the mentioned challenged used here for different application as stated before, are specifically textile tags. There are two types of textiles (Substrate) that have been used; cotton, which is organic in nature and stretchable synthetic textile, which is a mixture of viscose and polyester. The IC chip containing the information is attached to the antenna that is designed on the substrate which is acting as a Tag (Sensor), one with glue and the other with embroidery. The most specific part is the tag is embroidered with silver thread, which is conductive in nature. Hence embroidery is the fabrication method as well as the vital part of making the tags. The embroidery is accomplished with the help of domestic sewing machine. To get different results, different embroidery designs have been used; single line (less dense), horizontal embroidery and vertical embroidery. Moreover, six tags are fabricated using cotton substrate and two tags are fabricated using stretchable substrate, both substrates have IC antenna attached with sewing as well as glue as mentioned before. When the fabricated sensors (Tags) were tested in the anechoic chamber, all the sensors have different behavior with different read ranges as well as different peak frequencies. The objective was to test the humidity/moisture evaluation on the sensors. Hence, the sensors were very well exposed to the moisture and were tested again. The sensors with less dense embroidery (Single Line) were wetter than the dense embroidery (vertical and horizontal designs), hence, making the frequency more affected in terms of putting the frequency at a lower level in the less dense embroidered sensors than the dense ones. After being dried up, after 48 hours, the sensors were almost back the initial read range values. Therefore, the frequency difference between the initial read ranges and the moist read ranges is of vital importance and all the tags are having different behaviors. As the tags are textile in nature and are embroidered like a simple cloth, they are easy to wear and have very better contact with the body to have better results in terms of moisture evaluation. So further fabrication technique in the prospect of UHF RFID has multiple applications e.g. wounds sensor inside the bandages, soil moisture sensor, moisture/humidity leakage sensor etc. Hence, they have very vital advantages, which include that they are passive, cost-effective, and simple

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

Wearable sensors for respiration monitoring: a review

This paper provides an overview of flexible and wearable respiration sensors with emphasis on their significance in healthcare applications. The paper classifies these sensors based on their operating frequency distinguishing between high-frequency sensors, which operate above 10 MHz, and low-frequency sensors, which operate below this level. The operating principles of breathing sensors as well as the materials and fabrication techniques employed in their design are addressed. The existing research highlights the need for robust and flexible materials to enable the development of reliable and comfortable sensors. Finally, the paper presents potential research directions and proposes research challenges in the field of flexible and wearable respiration sensors. By identifying emerging trends and gaps in knowledge, this review can encourage further advancements and innovation in the rapidly evolving domain of flexible and wearable sensors.This work was supported by the Spanish Government (MICINN) under Projects TED2021-131209B-I00 and PID2021-124288OB-I00.Peer ReviewedPostprint (published version

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

Design and Development of Efficient and Conformal Printed Antennas for Wireless Sensing and Wearable Applications

Future wireless technologies would require flexibility from electronics that will enable the electronic components to adapt according to the everyday use environment. Flexible electronics has been used in many wireless sensing and wearable applications. One of the fastest growing wireless technologies of this decade is Radio Frequency Identification (RFID) which is an automatic identification technology that uses electromagnetic interaction to identify, sense and track people or objects with transponders known as tags. RFID is rapidly replacing the bar code technology in supply chain applications and huge amount of tags are needed to be produced in order to meet the needs of this application. The production method and material selection are few of the key parameters which are under study for the cost-effective and efficient fabrication of RFID tags and wearable antennas. The latest manufacturing technologies such as inkjet, thermal and three dimensional (3D) printing have shown good potential in improving the fabrication process, however they need to be optimized and explored further to get the best possible results.This thesis reports the use of novel manufacturing methods for the development of passive Ultra High Frequency (UHF) RFID tags and wearable antennas on versatile substrates. Commercially available as well as 3D printed flexible substrates along with different conductive inks/pastes are used for the improvement in the fabrication process. The first part of the research compares inkjet and thermal printing for the RFID fabrication in detail and suggests suitable optimizing parameters for the materials under study. The second part of the research focuses on 3D printing of the substrates and then utilizing brush painting, 3D dispensing and embroidery process to improve the overall fabrication. In addition, the fabricated antennas are tested for humidity, bending and stretching for specific applications.The results indicate that the approach and methodologies used have great potential in improving the fabrication of RFID tags and antennas. The fabricated tags show excellent results and achieve the required performance for modern RFID applications such as supply chain, wearable biomedical sensing and environment monitoring. This detailed study will be very helpful to find out appropriate materials for fabricating wireless components with the best possible results, i.e. easy to fabricate, reliable and better wireless performance, for future applications such as Internet of Things (IoT) and smart RFID packaging

Desenho de antenas para sensores passivos em materiais não convencionais

Doutoramento em Engenharia EletrotécnicaMotivado pela larga expansão dos sistemas RFID e com o desenvolvimento do conceito de Internet das Coisas, a evolução no desenho e métodos de produção de antenas em suportes de materiais alternativos tem tido uma exploração intensiva nos últimos anos. Isto permitiu, não só o desenvolvimento de produtos no campo da interação homem-máquina, mas também tornar estes produtos mais pequenos e leves. A procura de novas técnicas e métodos para produzir eletrónica impressa e antenas em materiais alternativos e, portanto, uma porta aberta para o aparecimento de novas tecnologias. Isto aplica-se especialmente no mercado dos sensores, onde o peso, o tamanho, o consumo energético, e a adaptabilidade a diversos ambientes, têm grande relevância. Esta tese foca-se no desenvolvimento de antenas com suporte em materiais não convenvionais, como os já testados papel e têxteis, mas também na exploração de outros, desconhecidos do ponto de vista eléctrico, como a cortiça e polímeros biodegradáveis usados em impressão 3D. Estes materiais são portanto usados como substrato, ou material de suporte, para diversas antenas e, como tal, as propriedades electromagnéticas destes materiais têm de ser determinadas. Assim, e apresentado neste documento uma revisão de métodos de caracterização de materiais, bem como a proposta de um método baseado em linhas de trasmissão impressas, e a respectiva caracterização electromagnética de diversos materiais. Além disso, são propostos desenhos de antenas para diversos cenários e aplicações utilizando os materiais anteriormente mencionados. Com esta tese concluiu-se que a utilização de materiais alternativos e hoje uma realidade e os resultados obtidos são muito encorajodares para o desenvolvimento de um conjunto de sensores para aplicações RFID com uma grande capacidade de integração.The advancement of the design and fabrication of antennas using textiles or paper as substrates has rapidly grown motivated by the boom of RFID systems and the developing concept of the Internet of Things. These advancements have allowed, not only the development of products for manmachine interaction, but also to make these products smaller and lighter. The search for new techniques and methods to produce printed electronics and antennas in alternative materials is therefore an open door for new technologies to emerge. Especially in the sensors market, where weight, size, power consumption and the adaptability to the target application, are of great importance. This thesis focuses on the development of antenna design approaches with alternative materials, such as the already tested paper and textiles, but also others relatively unknown, such as cork and biodegradable polymers used in 3D printing. These materials are applied to act as substrates, or support structures for the antennas. Therefore, their electromagnetic properties need to be determined. Due to that, a review of electromagnetic characterization methods, as well as the proposal of a custom method based on printed transmission lines, is presented in this document. Besides, several antenna designs, for di erent application scenarios, using the previously mentioned materials, are proposed. With this thesis it was proved that it is possible to develop passive sensors in di erent alternative materials for RFID applications and others, which shows great promise in the use of these materials to achieve higher integration in sensing and identi cation applications