A Historical Review of the Development of Electronic Textiles

From Nature to Technology: Exploring the Potential of Plant-Based Materials and Modified Plants in Biomimetics, Bionics, and Green Innovations

This review explores the extensive applications of plants in areas of biomimetics and bioinspiration, highlighting their role in developing sustainable solutions across various fields such as medicine, materials science, and environmental technology. Plants not only serve essential ecological functions but also provide a rich source of inspiration for innovations in green nanotechnology, biomedicine, and architecture. In the past decade, the focus has shifted towards utilizing plant-based and vegetal waste materials in creating eco-friendly and cost-effective materials with remarkable properties. These materials are employed in making advancements in drug delivery, environmental remediation, and the production of renewable energy. Specifically, the review discusses the use of (nano)bionic plants capable of detecting explosives and environmental contaminants, underscoring their potential in improving quality of life and even in lifesaving applications. The work also refers to the architectural inspirations drawn from the plant world to develop novel design concepts that are both functional and aesthetic. It elaborates on how engineered plants and vegetal waste have been transformed into value-added materials through innovative applications, especially highlighting their roles in wastewater treatment and as electronic components. Moreover, the integration of plants in the synthesis of biocompatible materials for medical applications such as tissue engineering scaffolds and artificial muscles demonstrates their versatility and capacity to replace more traditional synthetic materials, aligning with global sustainability goals. This paper provides a comprehensive overview of the current and potential uses of living plants in technological advancements, advocating for a deeper exploration of vegetal materials to address pressing environmental and technological challenges.

Advances in Smart Photovoltaic Textiles

Energy harvesting textiles have emerged as a promising solution to sustainably power wearable electronics. Textile-based solar cells (SCs) interconnected with on-body electronics have emerged to meet such needs. These technologies are lightweight, flexible, and easy to transport while leveraging the abundant natural sunlight in an eco-friendly way. In this Review, we comprehensively explore the working mechanisms, diverse types, and advanced fabrication strategies of photovoltaic textiles. Furthermore, we provide a detailed analysis of the recent progress made in various types of photovoltaic textiles, emphasizing their electrochemical performance. The focal point of this review centers on smart photovoltaic textiles for wearable electronic applications. Finally, we offer insights and perspectives on potential solutions to overcome the existing limitations of textile-based photovoltaics to promote their industrial commercialization.

Fiber Integrated Metal-Organic Frameworks as Functional Components in Smart Textiles

Owing to high modularity and synthetic tunability, metal-organic frameworks (MOFs) on textiles are poised to contribute to the development of state-of-the-art wearable systems with multifunctional performance. While these composite materials have demonstrated promising functions in sensing, filtration, detoxification, and biomedicine, their applicability in multifunctional systems is only beginning to materialize. This review highlights the multifunctionality and versatility of MOF-integrated textile systems. It summarizes the operational goals of MOF@textile composites, encompassing sensing, filtration, detoxification, drug delivery, UV protection, and photocatalysis. Building upon these recent advances, this review concludes with an outlook on emerging opportunities for the diverse applications of MOF@textile systems in the realm of smart wearables.

Recent research trends in textile-based temperature sensors: a mini review

In this review, the current state of research on textile-based temperature sensors is explored by focusing on their potential use in various applications. The textile-based sensors show various advantages including flexibility, conformability and seamlessness for the wearer. Integration of the textile-based sensors into clothes or fabric-based products enables continuous and sensitive monitoring of change in temperature, which can be used for various medical and fitness applications. However, there are lacks of comprehensive review on the textile-based temperature sensors. This review introduces various types of textile-based temperature sensors, including resistive, thermoelectric and fibre-optical sensors. In addition, the challenges that need to be addressed to fully realise their potential, which include improving sensitivity and accuracy, integrating wireless communication capabilities, and developing low-cost fabrication techniques. The technological advances in textile-based temperature sensors to overcome the limitations will revolutionize wearable devices requiring function of temperature monitoring.

The Influence of the Washing Process on the Impedance of Textronic Radio Frequency Identification Transponder Antennas

Antennas dedicated to RFID systems created on textile substrates should maintain strictly defined parameters. During washing, the materials from which such antennas are made are exposed to mechanical and chemical exposure-degradation of the parameters characterizing those materials may occur, which in turn may lead to a change in the parameters of the antenna. For research purposes, four groups of model dipole antennas (sewn with two types of conductive threads on two fabrics) were created and then they were subjected to several washing processes. After each stage of the experiment, the impedance parameters of the demonstration antennas were measured using indirect measurements. Based on the obtained results, it was found that these parameters change their values during washing, and that this is influenced by a number of factors, e.g., shrinkage of the substrate fabric.

Electronic textiles: New age of wearable technology for healthcare and fitness solutions

Sedentary lifestyles and evolving work environments have created challenges for global health and cause huge burdens on healthcare and fitness systems. Physical immobility and functional losses due to aging are two main reasons for noncommunicable disease mortality. Smart electronic textiles (e-textiles) have attracted considerable attention because of their potential uses in health monitoring, rehabilitation, and training assessment applications. Interactive textiles integrated with electronic devices and algorithms can be used to gather, process, and digitize data on human body motion in real time for purposes such as electrotherapy, improving blood circulation, and promoting wound healing. This review summarizes research advances on e-textiles designed for wearable healthcare and fitness systems. The significance of e-textiles, key applications, and future demand expectations are addressed in this review. Various health conditions and fitness problems and possible solutions involving the use of multifunctional interactive garments are discussed. A brief discussion of essential materials and basic procedures used to fabricate wearable e-textiles are included. Finally, the current challenges, possible solutions, opportunities, and future perspectives in the area of smart textiles are discussed.

Conductive Textiles for Signal Sensing and Technical Applications

Conductive textiles have found notable applications as electrodes and sensors capable of detecting biosignals like the electrocardiogram (ECG), electrogastrogram (EGG), electroencephalogram (EEG), and electromyogram (EMG), etc; other applications include electromagnetic shielding, supercapacitors, and soft robotics. There are several classes of materials that impart conductivity, including polymers, metals, and non-metals. The most significant materials are Polypyrrole (PPy), Polyaniline (PANI), Poly(3,4-ethylenedioxythiophene) (PEDOT), carbon, and metallic nanoparticles. The processes of making conductive textiles include various deposition methods, polymerization, coating, and printing. The parameters, such as conductivity and electromagnetic shielding, are prerequisites that set the benchmark for the performance of conductive textile materials. This review paper focuses on the raw materials that are used for conductive textiles, various approaches that impart conductivity, the fabrication of conductive materials, testing methods of electrical parameters, and key technical applications, challenges, and future potential.

Fabrication of Conductive Fabrics Based on SWCNTs, MWCNTs and Graphene and Their Applications: A Review

In recent years, the field of conductive fabrics has been challenged by the increasing popularity of these materials in the production of conductive, flexible and lightweight textiles, so-called smart textiles, which make our lives easier. These electronic textiles can be used in a wide range of human applications, from medical devices to consumer products. Recently, several scientific results on smart textiles have been published, focusing on the key factors that affect the performance of smart textiles, such as the type of substrate, the type of conductive materials, and the manufacturing method to use them in the appropriate application. Smart textiles have already been fabricated from various fabrics and different conductive materials, such as metallic nanoparticles, conductive polymers, and carbon-based materials. In this review, we study the fabrication of conductive fabrics based on carbon materials, especially carbon nanotubes and graphene, which represent a growing class of high-performance materials for conductive textiles and provide them with superior electrical, thermal, and mechanical properties. Therefore, this paper comprehensively describes conductive fabrics based on single-walled carbon nanotubes, multi-walled carbon nanotubes, and graphene. The fabrication process, physical properties, and their increasing importance in the field of electronic devices are discussed.

An Investigation into the Adsorption Mechanism of Organic Anions on a New Spandex

In recent years, there has been significant interest in the study of spandex in high-elasticity sensors. As a new kind of special spandex, dyeable spandex shows strong adsorption capacity for anions. In this study, neutral red G was used as an anion adsorption simulator to study the adsorption mechanism of dyeable spandex on anionic materials. The structure of dyeable spandex was characterized by the modern instrumental analysis method, and the adsorption kinetics and thermodynamics of neutral red G on dyeable spandex were discussed. The results show that the use of mixed amines as chain extenders for dyeable spandex reduced the regularity of molecules and the crystallinity of spandex, which was beneficial to the diffusion adsorption of anions. On the other hand, the number of secondary amino groups increased, providing more adsorption sites under acidic conditions. The adsorption of neutral red G on dyeable spandex satisfied the quasi-second-order kinetics and the Langmuir adsorption model, indicating that dye adsorption on spandex was mainly electrostatic. The diffusion coefficient and equilibrium adsorption capacity of neutral red G on dyeable spandex increased significantly, whereas enthalpy and entropy decreased.

Development and Characterization of Embroidery-Based Textile Electrodes for Surface EMG Detection

The interest in wearable devices has expanded to measurement devices for building IoT-based mobile healthcare systems and sensing bio-signal data through clothing. Surface electromyography, called sEMG, is one of the most popular bio-signals that can be applied to health monitoring systems. In general, gel-based (Ag/AgCl) electrodes are mainly used, but there are problems, such as skin irritation due to long-time wearing, deterioration of adhesion to the skin due to moisture or sweat, and low applicability to clothes. Hence, research on dry electrodes as a replacement is increasing. Accordingly, in this study, a textile-based electrode was produced with a range of electrode shapes, and areas were embroidered with conductive yarn using an embroidery technique in the clothing manufacturing process. The electrode was applied to EMG smart clothing for fitness, and the EMG signal detection performance was analyzed. The electrode shape was manufactured using the circle and wave type. The wave-type electrode was more morphologically stable than the circle-type electrode by up to 30% strain, and the electrode shape was maintained as the embroidered area increased. Skin-electrode impedance analysis confirmed that the embroidered area with conductive yarn affected the skin contact area, and the impedance decreased with increasing area. For sEMG performance analysis, the rectus femoris was selected as a target muscle, and the sEMG parameters were analyzed. The wave-type sample showed higher EMG signal strength than the circle-type. In particular, the electrode with three lines showed better performance than the fill-type electrode. These performances operated without noise, even with a commercial device. Therefore, it is expected to be applicable to the manufacture of electromyography smart clothing based on embroidered electrodes in the future.

A New Class of Electronic Devices Based on Flexible Porous Substrates

With the advent of the Internet of Things era, the connection between electronic devices and humans is getting closer and closer. New-concept electronic devices including e-skins, nanogenerators, brain-machine interfaces, and implantable medical devices, can work on or inside human bodies, calling for wearing comfort, super flexibility, biodegradability, and stability under complex deformations. However, conventional electronics based on metal and plastic substrates cannot effectively meet these new application requirements. Therefore, a series of advanced electronic devices based on flexible porous substrates (e.g., paper, fabric, electrospun nanofibers, wood, and elastic polymer sponge) is being developed to address these challenges by virtue of their superior biocompatibility, breathability, deformability, and robustness. The porous structure of these substrates can not only improve device performance but also enable new functions, but due to their wide variety, choosing the right porous substrate is crucial for preparing high-performance electronics for specific applications. Herein, the properties of different flexible porous substrates are summarized and their basic principles of design, manufacture, and use are highlighted. Subsequently, various functionalization methods of these porous substrates are briefly introduced and compared. Then, the latest advances in flexible porous substrate-based electronics are demonstrated. Finally, the remaining challenges and future directions are discussed.

Influence of Sweat on Joint and Sensor Reliability of E-Textiles

This article addresses reliability under the sweat of interconnection techniques for the mounting surface mounted device (SMD) components and fully printed humidity sensors onto conductive stretchable textile ribbons. Samples underwent testing for the effect of ageing by artificial sweat on their electrical resistance using both alkaline and acidic artificial sweat. The best results in terms of electrical resistance change were obtained for samples soldered to the conductive fibers interwoven in the ribbon. However, this method can damage the ribbon due to the high temperature during soldering and significantly reduce the mechanical properties and flexibility of the ribbon, which can lead to a limited service life of samples. On the other hand, adhesive bonding is a very interesting alternative, where the above-mentioned properties are preserved, but there is a significant effect of sweat ageing on electrical resistance. The results of fully printed graphene-based humidity sensors show that, for the intended use of these sensors (i.e., detection of changes in moisture on the human body), usage of the samples is possible, and the samples are sufficiently reliable in the case of sweat degradation. In addition, the response of the sensor to humidity is quite high: 98% at a relative humidity of 98%.

Advanced sensor technologies and the future of work

Exposure science is fundamental to the field of occupational safety and health. The measurement of worker exposures to hazardous agents informs effective workplace risk mitigation strategies. The modern era of occupational exposure measurement began with the invention of the personal sampling device, which is still widely used today in the practice of occupational hygiene. Newer direct-reading sensor devices are incorporating recent advances in transducers, nanomaterials, electronics miniaturization, portability, batteries with high-power density, wireless communication, energy-efficient microprocessing, and display technology to usher in a new era in exposure science. Commercial applications of new sensor technologies have led to a variety of health and lifestyle management devices for everyday life. These applications are also being investigated as tools to measure occupational and environmental exposures. As the next-generation placeable, wearable, and implantable sensor technologies move from the research laboratory to the workplace, their role in the future of work will be of increasing importance to employers, workers, and occupational safety and health researchers and practitioners. This commentary discusses some of the benefits and challenges of placeable, wearable, and implantable sensor technologies in the future of work.

Application of self-adhesive conductive material on textiles

A basic overview of electronics on textiles is given with an emphasis on self-adhesive conductive materials and their characteristics. It is kept on materials, self-adhesive conductive textiles and metal tapes and foils, which can be easily obtained. Their advantages compared to other techniques for electronics on textiles are described. The proposed structure is for the microwave area, which is a demanding area with regard to high frequencies.

Advanced Functional Materials for Intelligent Thermoregulation in Personal Protective Equipment

The exposure to extreme temperatures in workplaces involves physical hazards for workers. A poorly acclimated worker may have lower performance and vigilance and therefore may be more exposed to accidents and injuries. Due to the incompatibility of the existing standards implemented in some workplaces and the lack of thermoregulation in many types of protective equipment that are commonly fabricated using various types of polymeric materials, thermal stress remains one of the most frequent physical hazards in many work sectors. However, many of these problems can be overcome with the use of smart textile technologies that enable intelligent thermoregulation in personal protective equipment. Being based on conductive and functional polymeric materials, smart textiles can detect many external stimuli and react to them. Interconnected sensors and actuators that interact and react to existing risks can provide the wearer with increased safety, protection, and comfort. Thus, the skills of smart protective equipment can contribute to the reduction of errors and the number and severity of accidents in the workplace and thus promote improved performance, efficiency, and productivity. This review provides an overview and opinions of authors on the current state of knowledge on these types of technologies by reviewing and discussing the state of the art of commercially available systems and the advances made in previous research works.

Textile-Based Sensors for Biosignal Detection and Monitoring

Biosignals often have to be detected in sports or for medical reasons. Typical biosignals are pulse and ECG (electrocardiogram), breathing, blood pressure, skin temperature, oxygen saturation, bioimpedance, etc. Typically, scientists attempt to measure these biosignals noninvasively, i.e., with electrodes or other sensors, detecting electric signals, measuring optical or chemical information. While short-time measurements or monitoring of patients in a hospital can be performed by systems based on common rigid electrodes, usually containing a large amount of wiring, long-term measurements on mobile patients or athletes necessitate other equipment. Here, textile-based sensors and textile-integrated data connections are preferred to avoid skin irritations and other unnecessary limitations of the monitored person. In this review, we give an overview of recent progress in textile-based electrodes for electrical measurements and new developments in textile-based chemical and other sensors for detection and monitoring of biosignals.

Review on the Integration of Microelectronics for E-Textile

Modern electronic textiles are moving towards flexible wearable textiles, so-called e-textiles that have micro-electronic elements embedded onto the textile fabric that can be used for varied classes of functionalities. There are different methods of integrating rigid microelectronic components into/onto textiles for the development of smart textiles, which include, but are not limited to, physical, mechanical, and chemical approaches. The integration systems must satisfy being flexible, lightweight, stretchable, and washable to offer a superior usability, comfortability, and non-intrusiveness. Furthermore, the resulting wearable garment needs to be breathable. In this review work, three levels of integration of the microelectronics into/onto the textile structures are discussed, the textile-adapted, the textile-integrated, and the textile-based integration. The textile-integrated and the textile-adapted e-textiles have failed to efficiently meet being flexible and washable. To overcome the above problems, researchers studied the integration of microelectronics into/onto textile at fiber or yarn level applying various mechanisms. Hence, a new method of integration, textile-based, has risen to the challenge due to the flexibility and washability advantages of the ultimate product. In general, the aim of this review is to provide a complete overview of the different interconnection methods of electronic components into/onto textile substrate.

A Facile Approach of Fabricating Electrically Conductive Knitted Fabrics Using Graphene Oxide and Textile-Based Waste Material

This research investigated a feasible approach to fabricating electrically conductive knitted fabrics using previously wet-spun wool/polyacrylonitrile (PAN) composite fibre. In the production of the composite fibre, waste wool fibres and PAN were used, whereby both the control PAN (100% PAN) and wool/PAN composite fibres (25% wool) were knitted into fabrics. The knitted fabrics were coated with graphene oxide (GO) using the brushing and drying technique and then chemically reduced using hydrazine to introduce the electrical conductivity. The morphological study showed the presence of GO sheets wrinkles on the coated fabrics and their absence on reduced fabrics, which supports successful coating and a reduction of GO. This was further confirmed by the colour change properties of the fabrics. The colour strength (K/S) of the reduced control PAN and wool/PAN fabrics increased by ~410% and ~270%, and the lightness (L*) decreased ~65% and ~71%, respectively, compared to their pristine fabrics. The Fourier transform infrared spectroscopy showed the presence and absence of the GO functional groups along with the PAN and amide groups in the GO-coated and reduced fabrics. Similarly, the X-ray diffraction analysis exhibited a typical 2θ peak at 10⁰ that represents the existence of GO, which was demolished after the reduction process. Moreover, the wool/PAN/reduced GO knitted fabrics showed higher electrical conductivity (~1.67 S/cm) compared to the control PAN/reduced GO knitted fabrics (~0.35 S/cm). This study shows the potential of fabricating electrically conductive fabrics using waste wool fibres and graphene that can be used in different application fields.

Non-Invasive Fetal Electrocardiogram Monitoring Techniques: Potential and Future Research Opportunities in Smart Textiles

During the pregnancy, fetal electrocardiogram (FECG) is deployed to analyze fetal heart rate (FHR) of the fetus to indicate the growth and health of the fetus to determine any abnormalities and prevent diseases. The fetal electrocardiogram monitoring can be carried out either invasively by placing the electrodes on the scalp of the fetus, involving the skin penetration and the risk of infection, or non-invasively by recording the fetal heart rate signal from the mother’s abdomen through a placement of electrodes deploying portable, wearable devices. Non-invasive fetal electrocardiogram (NIFECG) is an evolving technology in fetal surveillance because of the comfort to the pregnant women and being achieved remotely, specifically in the unprecedented circumstances such as pandemic or COVID-19. Textiles have been at the heart of human technological progress for thousands of years, with textile developments closely tied to key inventions that have shaped societies. The relatively recent invention of smart textiles is set to push boundaries again and has already opened the potential for garments relevant to medicine, and health monitoring. This paper aims to discuss the different technologies and methods used in non-invasive fetal electrocardiogram (NIFECG) monitoring as well as the potential and future research directions of NIFECG in the smart textiles area.

Metallisation of Textiles and Protection of Conductive Layers: An Overview of Application Techniques

The rapid growth in wearable technology has recently stimulated the development of conductive textiles for broad application purposes, i.e., wearable electronics, heat generators, sensors, electromagnetic interference (EMI) shielding, optoelectronic and photonics. Textile material, which was always considered just as the interface between the wearer and the environment, now plays a more active role in different sectors, such as sport, healthcare, security, entertainment, military, and technical sectors, etc. This expansion in applied development of e-textiles is governed by a vast amount of research work conducted by increasingly interdisciplinary teams and presented systematic review highlights and assesses, in a comprehensive manner, recent research in the field of conductive textiles and their potential application for wearable electronics (so called e-textiles), as well as development of advanced application techniques to obtain conductivity, with emphasis on metal-containing coatings. Furthermore, an overview of protective compounds was provided, which are suitable for the protection of metallized textile surfaces against corrosion, mechanical forces, abrasion, and other external factors, influencing negatively on the adhesion and durability of the conductive layers during textiles' lifetime (wear and care). The challenges, drawbacks and further opportunities in these fields are also discussed critically.

Vibration-Sensing Electronic Yarns for the Monitoring of Hand Transmitted Vibrations

Overexposure to hand transmitted vibrations (HTVs) from prolonged use of vibrating power tools can result in severe injuries. By monitoring the exposure of a worker to HTVs, overexposure, and injury, can be mitigated. An ideal HTV-monitoring system would measure vibration were it enters the body, which for many power tools will be the palm and fingers, however this is difficult to achieve using conventional transducers as they will affect the comfort of the user and subsequently alter the way that the tool is held. By embedding a transducer within the core of a textile yarn, that can be used to produce a glove, vibration can be monitored close to where it enters the body without compromising the comfort of the user. This work presents a vibration-sensing electronic yarn that was created by embedding a commercially available accelerometer within the structure of a yarn. These yarns were subsequently used to produce a vibration-sensing glove. The purpose of this study is to characterize the response of the embedded accelerometer over a range of relevant frequencies and vibration amplitudes at each stage of the electronic yarn's manufacture to understand how the yarn structure influences the sensors response. The vibration-sensing electronic yarn was subsequently incorporated into a fabric sample and characterized. Finally, four vibration-sensing electronic yarns were used to produce a vibration-sensing glove that is capable of monitoring vibration at the palm and index finger.

A Review of Solar Energy Harvesting Electronic Textiles

An increased use in wearable, mobile, and electronic textile sensing devices has led to a desire to keep these devices continuously powered without the need for frequent recharging or bulky energy storage. To achieve this, many have proposed integrating energy harvesting capabilities into clothing: solar energy harvesting has been one of the most investigated avenues for this due to the abundance of solar energy and maturity of photovoltaic technologies. This review provides a comprehensive, contemporary, and accessible overview of electronic textiles that are capable of harvesting solar energy. The review focusses on the suitability of the textile-based energy harvesting devices for wearable applications. While multiple methods have been employed to integrate solar energy harvesting with textiles, there are only a few examples that have led to devices with textile properties.

The Wearable Co-Design Domino: A User-Centered Methodology to Co-Design and Co-Evaluate Wearables

This paper presents a user-centered methodology to co-design and co-evaluate wearables that has been developed following a research-through design methodology. It has been based on the principles of human–computer interaction and on an empirical case entitled “Design and Development of a Low-Cost Wearable Glove to Track Forces Exerted by Workers in Car Assembly Lines” published in Sensors. Insights from both studies have been used to develop the wearable co-design domino presented in this study. The methodology consists of different design stages composed of an ideation stage, digital service development and test stages, hardware development and test stage, and a final test stage. The main conclusions state that it is necessary to maintain a close relationship between human factors and technical factors when designing wearable. Additionally, through the several studies, it has been concluded that there is need of different field experts that should co-design and co-evaluate wearable iteratively and involving users from the beginning of the process.

Single-Layer Pressure Textile Sensors with Woven Conductive Yarn Circuit

Today, e-textiles have become a fundamental trend in wearable devices. Fabric pressure sensors, as a part of e-textiles, have also received much interest from many researchers all over the world. However, most of the pressure sensors are made of electronic fibers and composed of many layers, including an intermediate layer for sensing the pressure. This paper proposes the model of a single layer pressure sensor with electrodes and conductive fibers intertwined. The plan dimensions of the fabricated sensors are 14 x 14 mm, and the thickness is 0.4 mm. The whole area of the sensor is the pressure-sensitive point. As expected, results demonstrate an electrical resistance change from 283 Ω at the unload pressure to 158 Ω at the load pressure. Besides, sensors have a fast response time (50 ms) and small hysteresis (5.5%). The hysteresis will increase according to the pressure and loading distance, but the change of sensor loading distance is very small. Moreover, the single-layer pressure sensors also show high durability under many working cycles (20,000 cycles) or washing times (50 times). The single-layer pressure sensor is very thin and more flexible than the multi-layer pressure sensor. The structure of this sensor is also expected to bring great benefits to wearable technology in the future.

Wash Testing of Electronic Yarn

Electronically active yarn (E-yarn) pioneered by the Advanced Textiles Research Group of Nottingham Trent University contains a fine conductive copper wire soldered onto a package die, micro-electro-mechanical systems device or flexible circuit. The die or circuit is then held within a protective polymer packaging (micro-pod) and the ensemble is inserted into a textile sheath, forming a flexible yarn with electronic functionality such as sensing or illumination. It is vital to be able to wash E-yarns, so that the textiles into which they are incorporated can be treated as normal consumer products. The wash durability of E-yarns is summarized in this publication. Wash tests followed a modified version of BS EN ISO 6330:2012 procedure 4N. It was observed that E-yarns containing only a fine multi-strand copper wire survived 25 cycles of machine washing and line drying; and between 5 and 15 cycles of machine washing followed by tumble-drying. Four out of five temperature sensing E-yarns (crafted with thermistors) and single pairs of LEDs within E-yarns functioned correctly after 25 cycles of machine washing and line drying. E-yarns that required larger micro-pods (i.e., 4 mm diameter or 9 mm length) were less resilient to washing. Only one out of five acoustic sensing E-yarns (4 mm diameter micro-pod) operated correctly after 20 cycles of washing with either line drying or tumble-drying. Creating an E-yarn with an embedded flexible circuit populated with components also required a relatively large micro-pod (diameter 0.93 mm, length 9.23 mm). Only one embedded circuit functioned after 25 cycles of washing and line drying. The tests showed that E-yarns are suitable for inclusion in textiles that require washing, with some limitations when larger micro-pods were used. Reduction in the circuit’s size and therefore the size of the micro-pod, may increase wash resilience.

Modeling Electrical Percolation to optimize the Electromechanical Properties of CNT/Polymer Composites in Highly Stretchable Fiber Strain Sensors

A simulation model of electrical percolation through a three-dimensional network of curved CNTs is developed in order to analyze the electromechanical properties of a highly stretchable fiber strain sensor made of a CNT/polymer composite. Rigid-body movement of the curved CNTs within the polymer matrix is described analytically. Random arrangements of CNTs within the composite are generated by a Monte-Carlo simulation method and a union-find algorithm is utilized to investigate the network percolation. Consequently, the strain-induced resistance change curves are obtained in a wide strain range of the composite. In order to compare our model with experimental results, two CNT/polymer composite fibers were fabricated and tested as strain sensors. Their effective CNT volume fractions are estimated by comparing the experimental data with our simulation model. The results confirm that the proposed simulation model reproduces well the experimental data and is useful for predicting and optimizing the electromechanical characteristics of highly stretchable fiber strain sensors based on CNT/polymer composites.

Requirements for Durability Improvement of Conductive Patterns Permeated in Textiles under Cyclic Tensile Deformation

Conductive patterns on textiles are one of the key components for electronic textiles (E-textiles). The patterns with deeper permeation of inks into the textiles show better durability against cyclic tensile deformation. However, other requirements for improving the durability and the behavior of resistance under deformation are still unclear. In this study, the resistance during cyclic tensile deformation was measured with changing conditions, and the resistance variation was analyzed while considering the stress variation. Silver inks were printed on a plain weave, and the pattern width and tensile direction against weft yarns were changed. Measurements confirmed that the resistance increased less with wider pattern widths and when the tensile direction was horizontal to the axis of the weft yarns. Through scanning electron microscopy (SEM) observation, we also confirmed that the growth rate of cracks, at the crossing point of yarns, was changed by the tensile direction. These results indicate that the durability is improved when the electricity path redundancy within the pattern is robust, and the crack growth rate at the yarn crossing points is low. The analysis also confirmed both increasing and decreasing behavior of resistance during stretching in the cyclic tensile deformation, indicating the behavior results from the stress variation of a plain weave.

E-Textiles for Healthy Ageing

The ageing population has grown quickly in the last half century with increased longevity and declining birth rate. This presents challenges to health services and the wider society. This review paper considers different aspects (e.g., physical, mental, and social well-being) of healthy ageing and how health devices can help people to monitor health conditions, treat diseases and promote social interactions. Existing technologies for addressing non-physical (e.g., Alzheimer's, loneliness) and physical (e.g., stroke, bedsores, and fall) related challenges are presented together with the drivers and constraints of using e-textiles for these applications. E-textiles provide a platform that enables unobtrusive and ubiquitous deployment of sensors and actuators for healthy ageing applications. However, constraints remain on battery, integration, data accuracy, manufacturing, durability, ethics/privacy issues, and regulations. These challenges can only effectively be met by interdisciplinary teams sharing expertise and methods, and involving end users and other key stakeholders at an early stage in the research.

Fabrics and Garments as Sensors: A Research Update

Properties critical to the structure of apparel and apparel fabrics (thermal and moisture transfer, elasticity, and flexural rigidity), those related to performance (durability to abrasion, cleaning, and storage), and environmental effects have not been consistently addressed in the research on fabric sensors designed to interact with the human body. These fabric properties need to be acceptable for functionalized fabrics to be effectively used in apparel. Measures of performance such as electrical conductivity, impedance, and/or capacitance have been quantified. That the apparel/human body system involves continuous transient conditions needs to be taken into account when considering performance. This review highlights gaps concerning fabric-related aspects for functionalized apparel and includes information on increasing the inclusion of such aspects. A multidisciplinary approach including experts in chemistry, electronics, textiles, and standard test methods, and the intended end use is key to widespread development and adoption.

A Novel Method for Embedding Semiconductor Dies within Textile Yarn to Create Electronic Textiles

Electronic yarns (E-yarns) contain electronics fully incorporated into the yarn’s structure prior to textile or garment production. They consist of a conductive core made from a flexible, multi-strand copper wire onto which semiconductor dies or MEMS (microelectromechanical systems) are soldered. The device and solder joints are then encapsulated within a resin micro-pod, which is subsequently surrounded by a textile sheath, which also covers the copper wires. The encapsulation of semiconductor dies or MEMS devices within the resin polymer micro-pod is a critical component of the fabrication process, as the micro-pod protects the dies from mechanical and chemical stresses, and hermetically seals the device, which makes the E-yarn washable. The process of manufacturing E-yarns requires automation to increase production speeds and to ensure consistency of the micro-pod structure. The design and development of a semi-automated encapsulation unit used to fabricate the micro-pods is presented here. The micro-pods were made from a ultra-violet (UV) curable polymer resin. This work details the choice of machinery and methods to create a semi-automated encapsulation system in which incoming dies were detected then covered in resin micro-pods. The system detected incoming 0402 metric package dies with an accuracy of 87 to 98%.

Towards The Internet-of-Smart-Clothing: A Review on IoT Wearables and Garments for Creating Intelligent Connected E-Textiles

Technology has become ubiquitous, it is all around us and is becoming part of us. Together with the rise of the Internet-of-Things (IoT) paradigm and enabling technologies (e.g., Augmented Reality (AR), Cyber-Physical Systems, Artificial Intelligence (AI), blockchain or edge computing), smart wearables and IoT-based garments can potentially have a lot of influence by harmonizing functionality and the delight created by fashion. Thus, smart clothes look for a balance among fashion, engineering, interaction, user experience, cybersecurity, design and science to reinvent technologies that can anticipate needs and desires. Nowadays, the rapid convergence of textile and electronics is enabling the seamless and massive integration of sensors into textiles and the development of conductive yarn. The potential of smart fabrics, which can communicate with smartphones to process biometric information such as heart rate, temperature, breathing, stress, movement, acceleration, or even hormone levels, promises a new era for retail. This article reviews the main requirements for developing smart IoT-enabled garments and shows smart clothing potential impact on business models in the medium-term. Specifically, a global IoT architecture is proposed, the main types and components of smart IoT wearables and garments are presented, their main requirements are analyzed and some of the most recent smart clothing applications are studied. In this way, this article reviews the past and present of smart garments in order to provide guidelines for the future developers of a network where garments will be connected like other IoT objects: the Internet-of-Smart-Clothing.

Photodiodes embedded within electronic textiles

A novel photodiode-embedded yarn has been presented and characterized for the first time, offering new possibilities for applications including monitoring body vital signs (including heart rate, blood oxygen and skin temperature) and environmental conditions (light, humidity and ultraviolet radiation). To create an E-Textile integrated with electronic devices that is comfortable, conformal, aesthetically pleasing and washable, electronic components are best integrated within the structure of a textile fabric in yarn form. The device is first encapsulated within a protective clear resin micro-pod before being covered in a fibrous sheath. The resin micro-pod and covering fibres have a significant effect on the nature of light received by the photoactive region of the device. This work characterised the effects of both encapsulating photodiodes within resin micro-pods and covering the micro-pod with a fibrous sheath on the opto-electronic parameters. A theoretical model is presented to provide an estimate for these effects and validated experimentally using two photodiode types and a range of different resin micro-pods. This knowledge may have wider applications to other devices with small-scale opto-electronic components. Wash tests confirmed that the yarns could survive multiple machine wash and drying cycles without deterioration in performance.

Developing an Acoustic Sensing Yarn for Health Surveillance in a Military Setting

Overexposure to high levels of noise can cause permanent hearing disorders, which have a significant adverse effect on the quality of life of those affected. Injury due to noise can affect people in a variety of careers including construction workers, factory workers, and members of the armed forces. By monitoring the noise exposure of workers, overexposure can be avoided and suitable protective equipment can be provided. This work focused on the creation of a noise dosimeter suitable for use by members of the armed forces, where a discrete dosimeter was integrated into a textile helmet cover. In this way the sensing elements could be incorporated very close to the ears, providing a highly representative indication of the sound level entering the body, and also creating a device that would not interfere with military activities. This was achieved by utilising commercial microelectromechanical system microphones integrated within the fibres of yarn to create an acoustic sensing yarn. The acoustic sensing yarns were fully characterised over a range of relevant sound levels and frequencies at each stage in the yarn production process. The yarns were ultimately integrated into a knitted helmet cover to create a functional acoustic sensing helmet cover prototype.