Proceedings, 2019, E-Textiles 2019

This work presents an innovative solar energy harvesting fabric and demonstrates its suitability for powering wearable and mobile devices. A large solar energy harvesting fabric containing 200 miniature solar cells has been shown to charge a 110 mF textile supercapacitor bank within 37 s. A series of solar energy harvesting fabrics with different design features, such as using red or black fibres, were tested and compared to a commercially available flexible solar panel outside under direct sunlight. The results showed that the solar energy harvesting fabrics had power densities that were favorable when compared to the commercially available solar cell. Full article

Knitting a thin insulated metal wire simultaneously with elastic yarn in the round creates a coil with a self-inductance close to a wound coil. This knit is flexible and can be stretched, allowing the diameter of the coil to change, resulting in a change of its self-inductance. It is found that rib stitch gives the highest inductance but stocking stitch gives the highest variation of self-inductance with changing diameter. The feasibility of using the knitted coil for inductive plethysmography is demonstrated by simulated breathing in a baby jumper with knitted coils. Full article

The measurement of pressure at the skin is highly important for a number of human-based monitoring applications. This work presents a resistive knitted spacer pressure sensor for monitoring the pressure at the skin–clothing–seat interface for wheelchair users. The sensor has been characterized over a relevant range of pressures, and its hysteretic behavior has been analyzed. Preliminary work towards creating supporting hardware for recording pressure at multiple junctions across the sensor has been presented. Full article

Solar cells are an option for powering active electronics on textiles, but should be fully integrated to avoid compromising the flexibility and handle of the basic fabric. Photovoltaic (PV) cells conventionally use rigid silicon wafers but there are also thin-film options, although some are sensitive to moisture and oxygen, and others require processing temperatures outside the range of most flexible materials. The coating on textiles is also influenced by the fabric’s texture, elasticity, and surface roughness. The demands of a flexible structure affect the choice of the other parts of PV cells, namely their electrical contacts and any encapsulation layers. The two alternative routes to a textile PV design are—(i) coat the fabric with successive layers needed to make a sandwich device, or (ii) coat individual yarns with these layers and then process them into a fabric, e.g., by weaving. Full article

An electrode is a fundamental element used in many electrotherapy devices. This work presents a novel dry electrode made from carbon and silicone rubber materials for wearable electrotherapy applications. The electrode was mixed using a speed mixer and fabricated using stencil printing. This paper investigates the resistivity change of the electrode under the pressure from 0 mmHg to 32.4 mmHg; and the skin–electrode impendence with the current frequency from 20 Hz to 10,000 Hz. The resistivity of the novel dry electrode is 24.6 ± 1.5 Ω∙m when the pressure on electrode is 17.7 mmHg. The skin–electrode impedance reduced from 1001.6 Ω to 145.3 Ω when the frequency increased from 20 Hz to 10,000 Hz. Full article

Overexposure to hand-transmitted vibrations (HTVs) is a serious concern within industries that use vibrating power tools as HTVs can lead to severe and chronic injuries to the hand-arm system, which are preventable by limiting vibration exposure. This study presents a novel vibration-sensing electronic yarn (E-yarn) that can be used to monitor HTVs at the point-of-entry of the vibrations into the hand. The construction of the vibration-sensing E-yarn is described, with the vibration-sensing E-yarns being fully characterised at each stage of the manufacturing process to understand how the manufacturing stages affect the behaviour of the embedded sensor. The results show that there is no significant difference in the sensor response at each of the three stages in the E-yarn production over a range of frequencies and amplitudes relevant to HTVs. Full article

This paper proposes an integrated smart cycling system for assisted cycling, energy harvesting and wireless power transfer systems on a bicycle, an enabling platform for autonomous e-textiles-based sensing. The cyclist is assisted by a switched reluctance motor, which also acts as a switched reluctance generator that harvests a peak power of 7.5 W, at 10% efficiency during cycling to power on body sensors. To demonstrate wearable on-body sensing, a thin flexible CO₂ gas sensor filament, which can be woven in fabric, is presented and evaluated. Wearable inductive resonant wireless power transfer (WPT) is achieved using textile embroidered coils on the bicycle’s handle and cycling gloves, achieving more than 80% WPT efficiency from the bicycle to the cyclist’s clothing, useful for powering mobile on-body sensors. Full article

The degree of pollution in the environment increases because of the vehicular emissions such as carbon monoxide (CO) and nitrogen dioxide (NO₂) gases. To minimize the exposure levels, it is necessary for individuals to be able to determine for themselves the pollution levels of the environments they are in so that they can take the necessary precautions. Textile-based gas sensors are an emerging solution and this paper furthers the concept by investigating a novel method for encapsulating gas sensors in textiles. While encapsulation is required to improve the durability and lifetime of the sensors, it essential for their operation that the encapsulants do not reduce the sensitivity of the gas sensor. This paper investigates the selectivity of two different flexible and breathable thermoplastic encapsulants (Platilon^®U and Zitex G-104) for sensing carbon monoxide by observing the sensor response with and without the encapsulants. Results show that while the encapsulants both enable the sensor to still function, Platilon^®U reduces the sensor sensitivity, whereas Zitex G-104 has very little effect. Full article

A main barrier to widespread use of electrocardiography garments for long term heart monitoring of elderly and patients is a poor skin-electrode signal transfer because of a high contact impedance and sensitivity to movement. This leads to unwanted disturbances and errors in recorded signals when the patient moves or even breathe, affecting the reliability and quality of the signals especially for patients with dry/old skin. In two different projects at the University of Borås, we have developed two novel products to solve the above problem; (1) an ongoing project that has fabricated a reusable and sustainable electro-conductive adhesive applicable between the skin and high-porous textile electrodes, and (2) a patent-pending skin-electrode glue (BioEl Glue^®) which is a biocompatible electro-conductive water-soluble glue used between skin and low-porous textile electrodes. Full article

The mass commercialization of electronic textiles is currently hindered due to the lack of reliable manufacturing technologies of energy storing textiles. To incorporate energy storage as a part of a garment, it must be manufactured in a systematic manner, allowing the integration of multiple components of electronic textiles simultaneously. Aiming towards process automation, carbon-based screen-printing inks were formulated for textile supercapacitor applications, focusing on the effect of carbon additives in the electrochemical performance. Devices were assembled, and their electrochemical performance was assessed. The maximum areal power density obtained was 12 mW cm⁻² with an areal energy density of 1.08 × 10⁻³ mWh cm⁻². Full article

The weaving of flexible electronic filaments directly into the body of textiles during manufacture represents the state-of-the-art process for integrating electronic functionality into fabrics in a manner that obscures the presence of the electronics from the wearer. The reliability of emerging prototypes under typical stresses from washing and bending is primarily dependent on the durability of the electrical conductors and on their interconnections with the electronic components attached to them on polyimide filaments. To improve the durability of these filaments, this paper uses the classical beam theory to investigate the material characteristics (thickness and elastic modulus) and suitability of different encapsulations such as polyimide, polyurethane, mylar, and PEEK films for limiting the mechanical stress on the electrical conductors. Full article

Most E-textile research tends to fall within the arts or science disciplinary boundaries, despite E-textiles themselves being interdisciplinary in nature. This work explores how contemporary woven textile practice methodologies can play a role within interdisciplinary research, expanding the creative and technical applications of materials and technologies. A team of electronics, textiles, and fashion specialists was formed to design and make an illuminated jacket for use by cyclists. The jacket incorporated bespoke woven panels that integrated electronic yarns within the pattern. The development of this prototype raised questions about the use of craft practice methodologies in the development of new E-textiles. Full article

Functional electrical stimulation (FES) has been used to revitalise the muscles of people suffering from various kinds of injury. However, when human skin is incorporated into electrical circuits, it must not be treated as a passive component. Skin’s electrical properties must be known when electrodes deliver electrical stimulation to the body, whether by hydrogel electrodes or by electrodes embedded in apparel. Failure to address this issue increases the risk of skin burns due to too high current through the skin/electrode interface. We have demonstrated that there is a relationship between electrode size and measured voltage. The rise of voltage with a reduction of electrode size can be explained by the diminution of the skin contact area with resulting higher skin/electrode impedances. Thus, finding an electrical skin model that represents the behaviour of human skin is important for circuit design and the product development process. Full article

This paper presents research about design a textile-based stretch sensor for making a reliable sensing system for dance movement sensing. We examined sixteen textile-based conductive stretch sensors that were made with commercially produced conductive materials. Through the analysis of their sensitivity, linearity, hysteresis, responsiveness, and fatigue, a silver-plated conductive fabric, Technik-tex P130B, shows the best performance for dance movement sensing. Then, we tested the bonding technique, and washability of Technik-tex P130B-made sensors. The finding shows that bonding makes a noticeable impact on sensor performance. Both bonding and washing increase the sensor’s resistance. Technik-tex P130B on one side bonding has the best performance for dance movement sensing. This reliable and washable textile-based stretch sensor is utilised for dance bodysuit making for further development. Full article

This paper reports the design fabrication and characterization of a flexible supercapacitor fabricated in a single layer of polyester-cotton fabric. The fabric and flexible supercapacitors were implemented with spray coated inexpensive carbon electrodes and low hazardous ionic liquid electrolyte. The encapsulated devices demonstrated an area capacitance of 20.6 mF·cm⁻². Full article

Functional electrical stimulation is commonly used as a rehabilitation therapy to support the movement of individuals who have suffered traumatic spinal cord injury. Recently, there has been a focused interest on the development of textile electrodes, as they pose many benefits over traditional electrodes. This study presents design considerations and the feasibility of a wearable FES garment sleeve using flexible and extensible screen-printed electrodes. Full article

Designing high-efficiency antennas on textiles is fundamental for the development of wirelessly-connected smart garments. Furthermore, large antenna arrays could be used to receive or harvest directional and ambient radio-frequency (RF) power from the environment, thus enabling battery-free e-textiles. The key challenges that are hindering the realisation of high efficiency antennas lie in the dielectric properties of fabrics, the conductivity of their traces, and their low textile thickness. This work numerically and experimentally analyses different RF transmission line structures to establish the limitations of widely utilised antenna designs, such as the microstrip patch, and proposes alternative wearable antenna design based on coplanar waveguide (CPW) structures. It is demonstrated that by using a CPW, insertion losses in a 20 mm line can be minimized by up to 40% for the same substrate, as compared to a microstrip, at 30 GHz. A CPW monopole antenna is demonstrated with more than 80% efficiency on a lossy, thin, poly-cotton substrate. Moreover, it is shown that the efficiency of the CPW monopole is independent of the substrate’s thickness and type of fabric. Full article

In this paper, we introduce a new modality for capturing body postures and social behaviour. Vice versa, we propose a new application area for on-body textile sensors. We have developed “smart trousers” with embedded textile pressure sensors that allow for classification of a large variety of postural movements as well as interactional states. Random Forest models are used to investigate those. Here, we give an overview of the research conducted and discuss potential use cases of the presented design. Full article

Polypyrrole (PPy) fibre electrodes and their ability to sense paracetamol (as a model drug) in addition to interferents such as ascorbic acid and dopamine were studied. PPy was electrodeposited onto carbon fibre (CF) through electropolymerisation using cyclic voltammetry in the presence of two different counter anions: potassium nitrate (KNO₃) and sodium dodecyl sulfate (SDS). PPy with SDS as dopant could sense paracetamol with an oxidation peak at 0.55 V vs. Ag/AgCl. The limit of detection of this fibre sensor was found to be 1 µM with a linear range of 1–100 µM of paracetamol (R² = 0.985). Full article

Fiber and textile-based chemical sensors are emerging tools which target minimally invasive monitoring. Fiber-shaped electrodes are a versatile design for wearable applications since the fiber architecture allows for straightforward integration into textiles facilitating the principle of “wear-and-forget”. Skin and wound care would benefit from real-time pH monitoring, which can indicate wound health and the physiological condition of the skin. A further application of wearable chemical sensors is therapeutic drug monitoring. Full article

This paper demonstrates a novel design of textile-based triboelectric nanogenerator (TENG), which is compatible with standard textile manufacturing. The device can convert kinetic energy occurring during frictional contact between two dissimilar materials into electricity based on contact electrification and the electrostatic induction effect. The TENG can generate an RMS open-circuit voltage of 136 V, an RMS short-circuit current of 2.68 µA and a maximum RMS power of 125 µW (38.8 mW/m2). To demonstrate practical applications, the TENG was embedded into a lab coat. The energy is generated from the relative movement between the arm and torso. Its output was used to drive a digital watch, a wearable night-time warning indicator for pedestrians, a wireless transmitter and a pedometer. Full article

: A new form of inorganic printed electronics has been developed that allows for high speed production of solid-state lighting on flexible substrates. Light emitting diodes (LED) become more efficient as their size is decreased. However, the difficulties in making the electrical connection to micro LEDs has previously prevented these benefits being exploited outside the laboratory. Standard InGaN film, grown on a defined substrate (heteroepitaxy), was fabricated into micro LEDs (approx. 27 µm) and dispersed in a carrier fluid to form an ink, which can then be printed using established printing technologies. During printing and curing, the geometry of the individual micro LEDs causes them to orientate into a single preferential direction. Connections can then be made via further printed layers of conductive and dielectric ink to create flexible lamps consisting of areas of discrete LEDs. These lamps have low power consumption and high light output making them ideal for incorporating into garments and for packaging. The “Thunderstorm” dress (a Rainbow Winters project) was developed for the “Wired to Wear” exhibition in the Museum of Science and Industry, Chicago (MSI) to demonstrate the potential of this technology. The concept was to turn the wearer into a living representation of a thunderstorm. The concept had previously been realised in 2010 using electroluminescent elements (EL) to create a lightning flash in the panels of the dress. However, this required the wearer to carry high voltage devices, bulky electronics and heavy batteries. Instead, using inorganic printed LEDs afforded the potential to create a truly wearable piece of haute couture, using low voltages, miniature electronics and small batteries. The work reported here describes the fabrication technique used to create the micro LED lamps and the issues related to their integration into a piece of wearable technology. The lamps could be driven in such a way as to create a more realistic flash compared to the EL version. Other potential applications such as smart packaging, are also discussed. Full article