Eng. Proc., 2023, E-Textiles 2023

This work describes the fabrication and testing of an interdigitated capacitive sensor, embedded in a wearable e-textile for non-invasive in vivo monitoring. The sensor is sensitive to moisture changes within the stratum corneum layer (SC) of the skin. Testing is conducted by measuring the hydration state of the skin before and after the application of moisturizing agents to the SC, and the readings are mapped to a commercial gold standard measurement of skin hydration using the Corneometer^®. The results confirm that the interdigitated sensor can accurately detect the change in the hydration state of the SC with a sensitivity of 1.29 pF per arbitrary units of hydration. Full article

In this project, a smart knee sleeve was developed for the purpose of measuring a subject’s knee angle continually. The device is wireless and washable, making it suitable for rehabilitation at home. Two separate methods were incorporated onto a standard knee sleeve: a flexible silicone-based bend sensor and two IMUs. Each approach was evaluated, and testing was conducted on three subjects wearing the knee sleeve, using a reference video motion-tracking method. Squats were used as the exercise protocol for testing. The results showed that the flex sensor performed better for two of the three participants, with an average RMSE of 8.3 degrees, which is comparable to results from related research. Full article

Fabricating printed electronic inks that are highly stable on textile substrates has remained a challenge for researchers to fully achieve e-textiles for various sensing and health monitoring applications. This review reports progress in addressing challenges with conductive inks for e-textiles. Relevant studies highlight major achievements including developing stable carbon nanotube and graphene inks with consistent electrical properties, formulating silver nanowire inks with excellent conductivity and flexibility, and enhancing the adhesion of carbon nanotube inks to fabrics without pretreatment. Key findings show improved dispersion and biocompatibility of carbon nanotubes using silk protein, high stability of graphene inks in optimized solvents, and flexible semiconductor inks able to withstand bending. Overall, advances have expanded the capabilities of e-textile devices fabricated with conductive inks. Full article

A low-cost electronic yarn (e-yarn) fabricated with conductive yarns and light-emitting diodes (LEDs) for wearables is presented. As part of ongoing research to develop smart interactive pedestrian clothing, this work demonstrates the design and performance qualities of braided e-yarns to produce red lighting effects. The design process adopted a simple encapsulation process with adhesive tape and a heat contraction tube to secure stainless steel conductive threads to solder pads of the LEDs. These were arranged in series against two stainless steel conductive threads to provide single positive and negative terminals at both ends. The success of these low-cost, flexible, and strong (wash durability) braided e-yarns proved to be a major achievement for integration into woven fabrics for smart pedestrian safety clothing. These braided e-yarns producing the necessary lighting effects are a key safety feature for improving pedestrian visibility and driver recognition at night-time. Full article

Plasma Technology has proven to be the most effective eco-friendly method for the textile industry in improving surface adhesion. Two different silk fabrics, raw and degummed silk are treated by low-pressure glow discharge oxygen plasma to improve hydrophilic properties for better adhesion and coating process. Oxygen plasma can produce etching and formation of polar functional groups on the surface of the fabrics. The plasma conditions like voltage and working pressure are maintained constant with different exposure times. The plasma-exposed fabrics are characterized by SEM, XPS and adsorption tests. SEM reveals that the changes in the fabric surface are prominent for higher treatment time. According to the results of XPS, the oxygen-containing functional groups are increased after plasma treatment. The GO adsorption test indicates the enhancement of GO on the plasma-treated fabrics than untreated silk. The GO is prepared by the Modified Hummers method. The GO is coated on the plasma-treated silk fabrics by a dip coating method. The GO-coated silk fabrics are converted into RGO fabric by ascorbic acid as a reducing agent. Electrical conductivity measurement of the fabricated silk reveals that adequate current flows through it to glow an LED bulb. Full article

The critical need for accurate and non-invasive temperature monitoring is prevalent in extreme environments, such as scuba diving. Current temperature measurement technologies present limitations, prompting the development of innovative solutions. We propose the integration of embroidered wearable thermocouple sensors, demonstrating their versatility and reliability in real-time temperature monitoring. T-type thermocouples, embroidered onto fabric, offer flexibility in sensor placement, eliminating the need for skin attachment. The results indicate efficient temperature detection across different body areas, from 32.5 °C at extremities to 37.5 °C at the axial position. Testing in scuba diving conditions reveals potential applications, including overheating alerts and hypothermia prevention. This technology bridges the gap between temperature measurement and the challenges of underwater exploration, enhancing diver safety and data collection capabilities. Full article

The “Embroidery Triboelectric Nanogenerator” (E-TENG) is a wearable device that extracts energy from human motion by making use of the triboelectric phenomena, in addition to conductive fabric along with embroidery threads. One of the greatest ways to transform ambient vibrational energy from the human body is to use a wearable triboelectric energy harvester. In this study, different E-TENGs were developed using conductive fabric as an electrode and two different triboelectric yarns, 100% Polyester (electron donor) and Nylon 6,6 (electron receiver). To investigate the electrical outputs and energy-collecting potential of the ETENG, different stitch length and line spacing of embroidery TENG were investigated by testing samples in a specially manufactured tapping and sliding devices. The optimized wearable embroidery energy harvester effectively captured 72 μJ (12 V) of human motion energy in a 1 μF capacitor in 120 s and 307.5 μJ (24.8 V) of energy in a 1 μF capacitor by 1.5 Hz sliding motion in 300 s from an ETFS3.1 sample. A maximum of 4.5 μJ (3 V) was collected in a 1 μF capacitor from ETFS2.3 using a tapping machine for 520 s at a 2 Hz tapping motion and a 50 mm separation distance. The effects of the stitch length and line spacing in the embroidered structure on the electrical output performance of the embroidery energy-harvesting TENG were investigated. Full article

Embroidery, once a symbol of craftsmanship, has transformed into a cutting-edge technology blending tradition and innovation. This article delves into the multifaceted applications of embroidery technology in smart and e-textiles, showcasing its precision in integrating electronic components and PCBs and embroidering complete electrical circuits. Addressing challenges in reliability and mass production, the article provides research-backed solutions, offering guidelines for reliable embroidered interconnections and conductive traces. Positioned in mass production, embroidery’s automation and scalability seamlessly extend industrial practices to e-textiles, establishing this technique as a dynamic force shaping the future of smart-textile technology. Full article

A wearable ECG monitoring system was developed by integrating embroidered electrodes, and the collected ECG waveforms were comparable to those obtained using gelled Ag/AgCl electrodes. The R-peak amplitude was 2.09 mV with a 42.9 dB SNR for signals acquired using embroidered electrodes. The ECG signal quality was observed to improve with an increase in electrode size and holding pressure. ECG signals were recorded while the subject was in a walking condition, resulting in detectable waveforms with no missing R-peak and a 30.13 dB SNR which were comparable to signals acquired using standard gelled electrodes under the same conditions. Overall, these results are promising for developing an applicable wearable ECG monitoring system. Full article

The integration of sensors into garments has paved the way for human activity recognition (AR), enabling users to engage in extended human motion recordings. The inherent fluidity of loose clothing allows it to mirror the wearer’s movements. From a statistical standpoint, clothing captures additional valuable insights beyond rigid body motions, improving AR. This work demonstrates how fabric’s orientation, layering and width contribute to the enhanced performance of AR with clothing in periodic motion. Experiments are reported in which a scotch yoke and a KUKA robot manipulator are used to induce the periodic motion of fabric cloth at different frequencies. These reveal that clothing-attached sensors exhibit higher frequency classification accuracy among sensors with an improvement of 27% for perpendicular-oriented fabric, 18% for triple-layered fabric, and 9% for large-width fabric, exceeding that seen with rigid attached sensors. Full article

Three-component strain sensors based on helical auxetic yarn (HAY) structure were designed. HAYs comprise elastic core yarn, wrapped by the composition of multifilament Nylon 66 and conductive spun yarns with three different electrical resistance. The electromechanical behavior of samples was investigated. The cross-section of samples was studied to investigate the aerial density of conductive fibers at different strain ranges. The results indicated that gauge factors of HAY strain sensors significantly depend on the electrical resistance of the conductive component. Therefore, a new generation of efficient wearable textile-based strain sensors is introduced, based on the adjustable and flexible nature of the auxetic yarns. Full article

This study presents the development of an ultraviolet-C (UVC)-enabled smart bandage embedded with a temperature sensor, designed for the treatment and management of chronic wounds. The bandage also incorporates an RGB light-emitting diode (LED) and a microcontroller. It features a high-precision temperature sensor with an accuracy of ±0.1 °C for real-time wound temperature monitoring. The UVC LED is employed to eliminate bacteria on wound surfaces, while an RGB LED, controlled by a microcontroller, signals the need for treatment and any changes in wound temperature. The strip is etched on a 25 µm thick Kapton film to offer flexibility and comfort for wearing on the body and is seamlessly integrated into a cotton crepe bandage, forming a smart bandage. The embedded electronics are protected from wound exudates with a conformal polyurethane encapsulant film. Initial results indicate that the sensor achieves an accuracy of 97% in free space, inside a bandage, and on the human body. Full article

Flexible capacitive pressure sensors have been widely developed to be used in electronic skin, human movement, real-time health monitoring, and human–machine interactions. This paper introduces a Flexible Capacitive Pressure Sensor Array (FCPSA) that is designed to reduce costs and can be integrated into commercial textiles, e.g., insoles. The FCPSA comprises a five-layer sandwich structure. The bottom layer is a conductive layer, operating both as interference shielding and the common electrode for the distributed capacitive sensor array, with a polyester double-jersey-knitted fabric acting as the dielectric material, segmented carbon woven fabrics as the top electrodes in the array, a polymeric film for electrical and moisture isolation, and a foam placed on the surface to improve comfort. A system including three CPSs and a data acquisition device is established for real-time pressure monitoring. In the range of 0–100 kPa, a capacity increase of 35% is observed, the linearity of which depends on the elastic behavior of the dielectric layer. This sensor array can be utilized for real-time pressure monitoring. Full article

Printing electronics directly onto fabric to create e-textiles is a promising technology, but it is currently limited by the achievable printing resolution. The suitability of a bespoke reverse-offset printing system for use in printed e-textile devices has been explored because of the higher resolution it can achieve compared with alternatives such as screen printing, while still being scalable due to its roll-to-roll nature. The process has successfully achieved high-resolution patterns, as fine as 30 microns, on flexible polymer substrates suitable for lamination onto textiles and printing directly onto coated fabrics. The printing system comprises a gantry stage with a PDMS-coated roller and a base section that holds the cliché (patterned plate) and substrate. The system is controlled using LabVIEW software to ensure precise synchronization of the linear-stage movement and roller rotation. The results demonstrated a significant improvement in printing resolution compared to conventional methods such as screen and inkjet printing. This work showcases the potential of reverse-offset printing for fabricating advanced electronic devices on flexible substrates, creating new possibilities in the field of wearable technology. Full article

We present an approach for inspecting the composition of exhaled breath from data obtained from sensors integrated in a knitted garment. Simultaneous recordings were made for temperature, relative humidity, CO₂ and VOC, using sensors sewn in a smart mask and sensors in the garment that include two knitted respiratory inductive plethysmography coils and one accelerometer. We established that the correlation between signals obtained from the smart mask sensors and those from chest and abdomen movement is linear. A linear regression model on mean centralized data was used to train a linear model to predict CO₂ and VOC data in exhaled breath from sensor readings in the knitted garment only. Full article

The advancements of e-textiles have accelerated innovation in diverse fields such as wearable technology and safety but face several challenges in commercial viability. Within the field of Human–Computer Interaction (HCI), comprehensive textile knowledge is often underrated which could lead to issues with user-acceptability, and ununiformed design choices, neglecting the textile’s tactile qualities. Designers often overlook the balance between aesthetics and functionality, while manufacturing companies struggle with limited documentation and gaps between textile and hardware manufacturing. To facilitate multidisciplinary e-textile development, this study encourages the use of service blueprinting to enhance collaboration and knowledge transfer across disciplines, illustrated by a use case. Full article

The reliability of conductive yarns used for textiles is, among other things, affected by washing and sweating as well as mechanical issues. This leads to corrosion of the metal surface and to breaks. The aim of this work was to gain a better understanding of the influence of different materials (metal as well as non-conductive cores) on electrical behavior and material loss. Different yarns coated with copper, silver, NiCu and NiCuCo with nylon or polyester cores were investigated. The coating thickness as well as the grain distribution was modified. The temperature distribution, the displacements and the vacancy concentration in the metal grains were determined. Full article

This study examines the durability of stretchable conductive tracks on knitted fabrics. Two knitted fabrics with three designs of conductive tracks are tested to assess the fabric strain release and resistance change after a 50% elongation. The optimised design, made with all needle back jacquard knitting with sinusoidal conductive tracks, exhibits a 4% increase in fabric length and a 0.23 Ω (38.9%) increase in resistance. This e-textile is used to fabricate a sleeve with integrated functional electrical stimulation (FES) for stroke rehabilitation. The optimised electrode pattern, designed for stroke arm/hand rehabilitation, was achieved through co-design with stroke survivors and healthcare professionals. The prototype was tested on stroke survivors to assess stimulation comfort and ease of use. Tests have confirmed that the electrode sleeve (e-sleeve) is comfortable to wear and that stroke survivors are able to don and doff the e-sleeve using a single hand, facilitating independent home use. Full article

This paper presents research on flat textile pressure sensor characteristics that are advantageous for use in the surgical environment. Eight, 4 by 4 textile pressure matrices were subjected to sensor error testing to evaluate the sensor output differences on foam vs. no foam. The pressure matrices were tested using a compression tester while monitoring the voltage output. The errors analysed included the span, sensitivity, and nonlinearity. The findings show that for use in the surgical environment, prototypes two and three demonstrate better performances in the tests on foam, and both prototypes exhibit properties that are more suited for the surgical environment and warrant further prototype development. Full article

Knitted electrodes provide numerous advantages over the gel electrodes typically used in clinical practice when designing wearable Electrocardiogram (ECG) systems. They typically have enhanced durability, better textile integration and do not dry out. However, the higher skin/electrode impedance makes them susceptible to noise from electrical interference. Adding a buffer amplifier circuit close to the electrode, creating an ‘active’ electrode, is one way to mitigate this. However, the choice of where to integrate these amplifiers in the garment remains. Therefore, this work measured the signal-to-noise ratio (SNR) of an ECG output when comparing the distance between the electrode and the operational amplifier (op-amp) buffer and found that when the buffer was placed directly under a knitted electrode, the noise was lower than that seen with gel electrodes. This also provided information on the impact of distance on the SNR. Full article

This research paper recommends an electrode construction and integration technique for dry silver-based textile electrodes capturing electromyographic (EMG) signals. Three integration methods with two different conductive textiles were compared using two analysis methods; analysis was also conducted before and after six washing cycles. Six wearable arm bands with each of the design parameter combinations were worn on the biceps brachii muscle to capture EMG signals from three users under a controlled task both before any washing of the bands occurred and after four washing cycles were completed. Additionally, impedance measurements over six frequency bands were recorded after each washing cycle. Textile electrodes made of Shieldex Techniktex P180B using an extended electrode integration method were found to perform best. Full article

In the field of textile and fashion design, there is a growing desire to integrate interactive technologies into creative work. Traditional design education typically lacks support for material-oriented designers to develop electronic skills alongside their expertise in materials. There is a need to develop proper support for these designers to enter the world of electronic textiles (e-textiles). Our previous work introduced a material-centred e-textile learning approach through the development of a toolkit. This paper offers a glimpse into a design project made by our students, where digital functionality intertwines with physical design. It serves as a testament to the effectiveness of our approach in merging interactive technology concepts with material expertise, thereby aiding these designers in their creative endeavours. Full article

This paper investigates the utilisation of smart interactive products by millennial consumers in the fashion industry and how their perceptions and experiences influence the adoption of such products. To achieve this, it employs a generational perspective. It utilises Midgley and Dowling’s theory of predisposition to innovate as its theoretical framework, providing a comprehensive exploration of consumers’ experiences with these products. To bridge the gap in understanding consumers’ limited adoption of smart textile (ST) products, this research employs Interpretive Phenomenological Analysis (IPA). This methodological choice is driven by uncovering how real-life experiences impact consumer behaviour in this context. Expanding on previous work, the research comprised two separate qualitative studies utilising Interpretive Phenomenological Analysis (IPA). Participants interact with specific interactive smart textiles, namely, the Levi’s Jacket by Google. Participant recruitment utilised the snowballing method, which was adapted due to the constraints imposed by the COVID-19 pandemic. Full article

In this article, we show the first capacitive strain sensor using a four-component helical auxetic yarn (HAY) structure. We demonstrate a prototype sensor that achieves a gauge factor (GF) of up to two and compare our experimental results with a simple geometric model of the HAY system. In addition to a high sensitivity, this sensor configuration is easily manufactured, suitable for textile integration, and produces a repeatable response. Full article

In an era of sustainability and innovation, the textile industry faces the challenge of reimagining traditional materials and manufacturing for an eco-conscious future. This research presents the results from the mechanical testing of materials manufactured via a novel manufacturing process and is part of a wider project that merges filament and small electrical components within a novel mesh material, thus enhancing breathability and reducing fabric weight for cost-effective comfort. FOYSE (Fibre on Yarn Surface Entanglement) is the novel process that manufactures a fourth class of textile and, thus, responds to the textile industry’s needs by providing an innovative noninterlaced textile manufacturing process. This project explores FOYSE’s disruptive potential in e-textiles and sustainable mesh materials, offering innovative solutions. Full article

Laminating screen-printed, flexible transfers is a reliable method of creating electronic connections across a textile. However, their limited resolution means that it is not possible to solder on fine-pitched components. An alternative substrate, etched copper on polyimide is compatible with fine pitch components, but is unsuitable for use over large areas. This work examines methods of combining the two systems to produce e-textiles that combine both their benefits. Tensiometer tests showed that 3M 9087 double-sided tape was the most robust for attaching the polyimide, and electrical interconnects formed by overlapping the transfer on top of the polyimide circuit gave the most stable and lowest resistance connections. Full article

This study focuses on advancing sweat management in clothing using low-current operating textile electroosmotic pumps, which could be beneficial for microenvironments with restricted ventilation, such as the one between the skin and protective wear. These systems, employing silver–copper fabric electrodes, a polycarbonate membrane with microchannels, and an adhesive web, enabled directed liquid transport. The critical role of the adhesive layer preparation is emphasized, often overlooked in previous research. Various adhesive perforations were tested for their impact on the flow under current action, both with and against gravity. Specific adhesive application techniques are proposed, found to significantly influence the flow rate and textile assembly cohesion. The custom setup yielded flow rates of up to 8.8 ± 0.08 mg min⁻¹ cm⁻², suitable for diverse human sweat rates. Optimization hinges on the delicate balance between binding and the active surface areas of the adhesive. Full article

Textile-based electrodes offer several advantages such as washability, flexibility, and reusability. However, there are challenges when it comes to long-term, real-time continuous monitoring, particularly during self-administration situations which introduce severe motion artifacts. In response to these challenges, researchers have explored various moisture retaining filling textiles to enhance the sustainability of long-term EMG monitoring. This study focuses on comparing three alternative textile fillings: 3D knitted fabric, nonwoven fabric, and microfiber sandwiched between embroidered textile electrodes to evaluate their moisture retention performance and ability to record EMG. The developed electrodes are comprised of embroidered a polyamide-silver hybrid conductive thread, with the filling textiles sandwiched between this yarn and the support fabric and bobbin yarn. The support fabric is an elastic textile band. The creation of these electrodes utilized satin stitch techniques. Impedance characteristics were analysed using an IVI-UM setup with a two-electrode configuration. The electrodes were applied to the subject’s bicep muscles using the elastic strap with a pressure of 12 mmHg. The developed textile filled embroidered electrodes using the satin stitch technique exhibited better dry and wet electrode skin-contact impedance performance compared to the normal satin stitch-based embroidered electrodes against to (Ag/AgCl) electrodes. Further evaluation focused on assessing the long-term stability and wettability of the wet electrode conditions with various drying time. The wet 3D knit (W3D) large satin stitched sandwiched electrodes displayed lower impedance characteristics than those made with wet nonwoven (WNW), wet microfiber (WMF), and the dry embroidered electrodes, with worst performing the normal satin stitch embroidered electrode. It was observed that increasing drying time increases skin-contact impedance, emphasizing the significance of selecting the appropriate filling materials capable of retaining moisture comfort over extended periods. This choice is vital for achieving long-term EMG monitoring and maintaining low contact impedance, which directly impacts the signal quality. The study evaluated the effects of moisture retention time for each textile filling type on sustainable long-term EMG monitoring. Among the tested electrodes, the wet ring satin stitch 3D knit (W3D) sandwiched embroidered electrode out-performed the others WNW, and wet MF based sandwiched electrode achieving a signal-to-noise ratio of 54.93 dB and a root mean square of 0.195 mV, respectively, at the parametric values identified in the experiments. Full article

This work reports an encapsulated and flexible solid-state AIC screen printed on top of a polyester–cotton textile. The proposed zinc-ion capacitor (ZIC) arrays were fabricated on top of a polymer-coated polyester–cotton textile with solution-based processes and inexpensive electrodes and electrolyte materials. This battery achieved an energy density of 0.47 μWh·cm⁻² (per device area) or 0.51 mWh·cm⁻² (per active material area) in a galvanostatic cycling test between 0.1 V and 1.8 V. Full article

Commercial solar cells can be embedded between textile layers by laminating to harvest energy in e-textile applications. However, techniques for connecting conductive textile wires to flexible and solid solar cells have not been studied in depth. Based on the literature and experimental validation, this study proposes a stitching connection technique for solar textiles. The feasibility of stitching was experimentally validated. First, the textile wires were joined to flexible solar cells by stitching with a sewing machine, and then embedded between fabric layers with TPU-lamination to simulate a real set-up in e-textile application. The machine washing durability of textile solar cell components with stitch-connected conductive textile wires was successfully verified. Full article