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E-textiles have emerged as a fast-growing area in wearable technology for sports and fitness due to the soft and comfortable nature of textile materials and the capability for smart functionality to be integrated into familiar sports clothing. This review paper presents the roles of wearable technologies in sport and fitness in monitoring movement and biosignals used to assess performance, reduce injury risk, and motivate training/exercise. The drivers of research in e-textiles are discussed after reviewing existing non-textile and textile-based commercial wearable products. Different sensing components/materials (e.g., inertial measurement units, electrodes for biosignals, piezoresistive sensors), manufacturing processes, and their applications in sports and fitness published in the literature were reviewed and discussed. Finally, the paper presents the current challenges of e-textiles to achieve practical applications at scale and future perspectives in e-textiles research and development. [ABSTRACT FROM AUTHOR]

In this paper a three-dimensional model of a novel electronic package has been developed using Finite element analysis to evaluate the shear load, tensile, bending and thermal stresses. Simulations of a complete flexible flip chip electronic packaging method are performed to minimize stresses on the packaged electronic device to improve robustness and reliability. Three component under-fill adhesives (Loctite 4860, Loctite 480 and Loctite 4902) and three circuit substrate materials (Kapton, Mylar and PEEK) are compared and the optimal thickness of each is found by shear load, tensile load, bending test and thermal expansion simulations. A fixed die size of 3.5 mm × 8 mm × 0.53 mm has been simulated and evaluated experimentally under shear and bending load. The shear and bending experimental results show good agreement with the simulation results and verify the simulated optimal thickness of the adhesive layer. The Kapton substrate together with the Loctite 4902 adhesive were identified as the optimum in the simulation. The simulation of under-fill adhesive and substrate thickness identified an optimum configuration of a 0.045–0.052 mm thick substrate layer and a 0.042–0.045 mm thickness of the Loctite 4902 adhesive. The bending simulation has also been used to determine the neutral axis of the encapsulated electronic package in this paper, thus identifying the optimal material and thickness for the encapsulation layer of the package. [ABSTRACT FROM AUTHOR]

Electronic Textiles (e-textiles) should ideally be handled and cleaned like traditional textiles. Therefore, we can expect e-textiles to be machine washed or hand washed. As e-textiles enhance traditional fabrics with electronic functionality, any embedded microsystem i.e., flexible electronic circuits, will be expected to survive and show functionality after the e-textile has been washed multiple times to ensure the garment is practical. Therefore, the choice of encapsulation material for microsystems in a textile must be hydrophobic and offer minimal expansion when washed and ensure the electronics are undetectable when the textile is handled or cleaned. This paper evaluates five different base/curing agent mixing ratios—5:1, 7:1, 10:1, 15:1, and 20:1—of commercial polydimethylsiloxane (PDMS) as an electronic packaging encapsulation. Contact angle and aqueous permeability experiments were conducted to tailor the PDMS mixture specifically for washable e-textile applications. The experimental results show that 20:1 PDMS is the most suitable as it is sufficiently hydrophobic with minimal swelling in commercial washing machine trials. Following this, a 40.3 µm-thick 20:1 conformal encapsulation of PDMS upon an touch and proximity flexible circuit that can be integrated into textiles via knitting and/or weaving, was examined. Results show the washing spin speed is a crucial factor with washing cycle duration having minimal impact when determining circuit functionality survival. Overall, the e-textiles in this work survived between 10 and 15 washes with microscopic inspection of the circuits revealing failure of the external wires but not the PDMS encapsulation—suggesting its sufficient robustness and durability as a suitable encapsulation material for washable electronic textiles. [ABSTRACT FROM AUTHOR]

Despite the recent advances in textile antennas, in complete systems such as a rectenna, the efficiency of fully textile solutions has been over 46% lower than hybrid textile/rigid implementations. This article presents a fully textile rectenna for ultralow-power sub-μW/cm2 applications. A dual-polarized omnidirectional low-profile textile antenna is presented. The rectenna is based on a compact inductively matched rectifier. The textile-based rectifier occupies 0.22 cm2 and achieves a state-of-the-art power conversion efficiency (PCE) of 41.8% at −20 dBm, at 820 MHz, despite its lossy substrate. A triple-band rectifier is then designed and fabricated to show the scalability of the matching approach. The rectifier is characterized using a new figure of merit “average PCE” over a time period while charging a capacitor. Time-varying S-parameters are used to quantify the impact of the capacitor’s charge on the impedance matching. The rectifier directly charges a 1.32 mF capacitor up to 1 V in 0.41 and 4.5 s from 10 and 0 dBm, respectively. Wireless testing of the proposed rectenna demonstrates over 50% and 40% (PCE) below 1 μW/cm2 in space and on-body, respectively. The rectenna efficiently receives power from mismatched polarization and with a 360° half-power beamwidth. [ABSTRACT FROM AUTHOR]

A novel packaging method that enables the reliable mounting and protection of bare die within a textile yarn has been investigated. The reliability of electronic textiles is highly challenging given the flexibility of the fabric and the rigors of typical applications. Achieving reliable operation requires novel packaging approaches. In order to maximize the reliability and to minimize stresses in the electronic package, the die should be located as close as possible to the central axis of the overall assembly. The die is bonded to a bottom Kapton substrate that contains patterned conductive interconnects and bond pads forming the functional circuit. The circuit is protected by a molded Kapton film that has recesses formed where the die is located. This approach has been compared with three other traditional packaging technologies during washing, twisting, and cyclical bending tests. The novel electronic packaging method shows the best performance in all tests surviving up to 45 wash cycles. [ABSTRACT FROM AUTHOR]

This article reviews materials developed to enable energy harvesting from textiles. It includes energy harvesting from mechanical, thermal, and light sources, and covers materials employed into yarns that can be woven into the textile and films that are deposited onto the surface of the textile. The textile places challenging constraints on the materials, for example, by limiting processing temperatures to typically less than 150°C and presenting a rough, inconsistent surface profile. Example materials include a screen-printable low-temperature composite lead zirconate titanate polymer film and poly(vinylidene fluoride) polymer fibers, both of which have been shown to harvest mechanical energy from textiles. Thermoelectric solutions demonstrated thus far are limited and challenging to implement within a textile. Photovoltaic solutions include organic and dye-sensitized solar cells fabricated into functionalized yarns and as films spray-coated onto textiles. While numerous suitable example materials and textile devices have been demonstrated, work is still needed to develop these into practical energy-harvesting solutions. [ABSTRACT FROM PUBLISHER]

A method for packaging integrated circuit silicon die in thin flexible circuits has been investigated that enables circuits to be subsequently integrated within textile yarns. This paper presents an investigation into the required materials and component dimensions in order to maximize the reliability of the packaging method. Two die sizes of 3.5 \,\,\text mm \times 8 \,\,\text mm \times 0.53\,\, \text mm and 2 \,\,\text mm \times 2\,\,\text mm \times 0.1 \,\,\text mm have been simulated and evaluated experimentally under shear load and during bending. The shear and bending experimental results show good agreement with the simulation results and verify the simulated optimal thickness of the adhesive layer. Three underfill adhesives (EP30AO, EP37-3FLF, and Epo-Tek 301 2fl), three highly flexible adhesives (Loctite 4860, Loctite 480, and Loctite 4902), and three substrates (Kapton, Mylar, and PEEK) have been evaluated, and the optimal thickness of each is found. The Kapton substrate, together with the EP37-3FLF adhesive, was identified as the best materials combination with the optimum underfill and substrate thickness identified as 0.05 mm. [ABSTRACT FROM AUTHOR]

A planar electroluminescent (EL) lamp has been screen-printed directly on to woven polyester cotton fabric to create a smart fabric lamp. The EL lamp consists of six printed layers and has been produced in colours: light blue, dark blue, and orange. The printed structure has high durability whilst maintaining the flexible and breathable properties of the fabric. The printing process relies on an interface layer developed at the University of Southampton [1] to smooth the woven fabric surface where required, presenting a more homogenous surface than the underlying woven fabric for the subsequently printed functional layers. [ABSTRACT FROM AUTHOR]

Conductive textiles are fabrics that include conductive yarns woven into or conductive tracks printed on to the textiles. Conductive textiles have attracted significant attention, since they are fundamental for the integration of electronic functions to achieve wearable devices. Screen printing is a well-established and cost-effective fabrication method; it enables a versatile layout of conductive tracks. The limitation of the current screen-printed conductive textiles is low durability to weathering, abrasion and washing. This paper presents a process for producing a waterproof and durable conductive textile using only screen printing. A three functional layer design was used to fabricate the durable conductive tracks. Firstly, an interface layer was printed to provide a smooth surface for subsequent printing, under-side protection and electrical insulation. Next, a silver layer provided the conductive track and finally an encapsulation layer was printed on top to provide upper-side protection and electrical insulation. The printed silver tracks achieved maximum conductivity using a single print. The conductivity of the silver tracks returned to its original value when they were dried after soaking in water continuously for 24 hours. [ABSTRACT FROM PUBLISHER]

This paper presents a method to integrate and package an accelerometer within a textile to create an electronic textile (e-textile). The smallest commercially available accelerometer sensor (2 mm × 2 mm × 0.95 mm) is used in the e-textile and is fully integrated within the weave structure of the fabric itself, rendering it invisible to the wearer. The e-textile forms the basis of a wearable woven sleeve which is applied to arm and knee joint bending angle measurement. The integrated e-textile based accelerometer sensor system is used to identify activity type, such as walking or running, and count the total number of steps taken. Performance was verified by comparing measurements of specific elbow joint angles over the range of 0° to 180° with those obtained from a commercial bending sensor from Bend Labs and from a custom-built goniometer. The joint bending angles, measured by all three sensors, show good agreement with an error of less than ~1% of reading which provides a high degree of confidence in the e-textile sensor system. Subsequently, knee joint angles were measured experimentally on three subjects with each being tested three times on each of three activities (walking, running and climbing stairs). This allowed the minimum and maximum knee joint angles for each activity to be determined. This data is then used to identify activity type and perform step counting. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This paper presents research into a user-friendly electronic sleeve (e-sleeve) with integrated electrodes in an array for wearable healthcare. The electrode array was directly printed onto an everyday clothing fabric using screen printing. The fabric properties and designed structures of the e-sleeve were assessed and refined through interaction with end users. Different electrode array layouts were fabricated to optimize the user experience in terms of comfort, effectivity and ease of use. The e-sleeve uses dry electrodes to facilitate ease of use and the electrode array can survive bending a sufficient number of times to ensure an acceptable usage lifetime. Different cleaning methods (washing and wiping) have been identified to enable reuse of the e-sleeve after contamination during use. The application of the e-sleeve has been demonstrated via muscle stimulation on the upper limb to achieve functional tasks (e.g., hand opening, pointing) for eight stroke survivors. [ABSTRACT FROM AUTHOR]

This paper presents the development of a stretchable electronic textile (e-textile) and the design of a knee sleeve with integrated electrodes for wearable applications. The e-textile is achieved by laminating a printed conductive pattern onto knitted fabric, followed by printing a carbon rubber electrode layer on top of the conductive pads of the conductive pattern. The Young's modulus of two knitted stretchable fabrics, made of different textile yarns, is tested and their impact on the e-textile and garment properties is discussed. Four printed conductive track designs in the form of a straight line, a sine wave, a half circle, and a horseshoe are laminated on these fabrics. The four designs are investigated in terms of conductivity, change during stretching, relaxation after stretching, and wash durability. A snap connector, attached to each end of the conductive tracks, provides electronic interconnection. The e-textiles survive 100 wash cycles with a resultant maximum resistance increase of 1.44 times. A fitted knee sleeve, for use in wearable electrotherapy for knee joint pain management, is fabricated by laminating a conductive track in the optimal sinusoidal design and then printing carbon rubber electrodes on top. [Display omitted] • Introduce a method for measuring the stretchability in stretchable electronic textiles. • Evaluated the stretchability of four shaped tracks on knitted fabrics specifically for applications requiring a 50% strain. • Developed an electronic textile with the capability to withstand 100 cycles of washing. • Introduced pattern cutting techniques to the realm of wearable technology to enhance usability. • A fitted knee sleeve is fabricated by laminating an optimal sinusoidal track and printing carbon rubber electrodes on top. [ABSTRACT FROM AUTHOR]