Search

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.

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.

In this article, organic light-emitting electrochemical cells (OLECs) have been fabricated on a substrate consisting of a standard woven polyester cotton textile. The textile substrate is presmoothed by first screen printing an ultraviolet (UV) curable polyurethane layer, termed the interface layer. Solution-processed spray coating is then utilized to deposit all the functional layers on the textile to achieve fully spray-coated flexible OLECs. OLEC devices were initially fabricated on ITO-coated glass substrates for process optimization. Then, the OLECs were fabricated on flexible textile using the optimized spray coating process. Finally, both OLECs devices on the glass and textile substrates were encapsulated by stencil printing epoxy before testing in an ambient environment. The OLECs on ITO-coated glass exhibit a turn-on voltage of 3 V, a brightness level of 200 cd/m2 and a lifetime of at least 60 min. The OLECs on textile exhibit a turn-on voltage of 4 V, a brightness level of 80 cd/m2 level and a lifetime of at least 30 min. [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]

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]

This paper details the enhancements in the dielectric and piezoelectric properties of a low-temperature screen-printable piezoelectric nano-composite film on flexible plastic and textile substrates. These enhancements involved adding silver nano particles to the nano-composite material and using an additional cold isostatic pressing (CIP) post-processing procedure. These developments have resulted in a 18% increase in the free-standing piezoelectric charge coefficient d 33 to a value of 98 pC/N. The increase in the dielectric constant of the piezoelectric film has, however, resulted in a decrease in the peak output voltage of the composite film. The potential for this material to be used to harvest mechanical energy from a variety of textiles under compressive and bending forces has been evaluated theoretically and experimentally. The maximum energy density of the enhanced piezoelectric material under 800 N compressive force was found to be 34 J/m 3 on a Kermel textile. The maximum energy density of the enhanced piezoelectric material under bending was found to be 14.3 J/m 3 on a cotton textile. These results agree very favourably with the theoretical predictions. For a 10x10 cm piezoelectric element 100 µm thick this equates to 38 μJ and 14.3 μJ of energy generated per mechanical action respectively which is a potentially useful amount of energy. [ABSTRACT FROM AUTHOR]

This paper presents the optimization of a bismuth tellurium (Bi1.8Te3.2)–antimony tellurium (Sb2Te3)-based thermoelectric generator (TEG) fabricated by screen-printing technology on flexible polyimide (Kapton) and textile substrates. New formulations of screen printable thermoelectric pastes are presented with optimized composition, curing conditions, and printing parameters. The modifications of the thermoelectric materials enable them to be successfully deposited on flexible textile substrates. The optimized values of resistivity of the BiTe and SbTe thick films on Kapton were 9.97 \times 10^-3 and 3.57 \times 10^-3 ~\Omega \cdot \text cm , respectively. The measured figure of merit at room temperature was 0.135 and 0.095 for BiTe and SbTe thick films on Kapton, respectively. The dimension of each printed thermoleg was 20~\text mm \times 2~\text mm \times 70.5~\mu \textm . For the TEG on Kapton, the printed assembly comprising eight thermocouples was coiled up and generated a voltage of 26.6 mV and a maximum power output of 455.4 nW at a temperature difference of 20 °C. For a printed TEG on textile, the maximum power output reached 2 \mu \textW from the same temperature difference. [ABSTRACT FROM PUBLISHER]

This paper describes a process for fabricating active electrodes and flexible conductive tracks on woven textiles for use in electrocardiogram (ECG) monitoring systems. The process involves the screen and stencil printing of dielectric and conductive polymer pastes on to a textile substrate. Unlike previous printed active electrodes which are printed on non-woven textiles, this paper reports active electrodes which are printed on to a significantly more challenging woven textile by making use of a polymer interface paste that reduces the surface roughness of the underlying textile. The conductive paths supplying power to the electrodes and carrying the buffered signal to the amplifier are implemented with a screen printable silver polymer paste. The electrode material is a stencil printed carbon loaded rubber. The buffer amplifier, which converts high impedance signals into low impedance signals, is integrated into the electrode structure, reducing the area taken up by the components and improving comfort during wearing. These electrodes are compared to passive electrodes fabricated with the same process and also to commercially available Ag/AgCl electrodes in an ECG monitoring application when the monitored subject is stationary, walking and jogging. It is shown that the textile active electrodes provide significantly improved performance compared to textile passive electrodes and similar performance to the Ag/AgCl electrodes. [ABSTRACT FROM AUTHOR]

Highlights: [•] The development of a fabrication process for textile-based biopotential monitoring networks. [•] Discussion of the design of the electrode networks and the electrical resistance of connections and electrodes. [•] Demonstration of electrode networks in 3 applications: ECG, EMG on the forearm and combined EMG and EOG on a headband. [•] For each demonstrator system an example recording of the relevant signal or signals is included. [•] A discussion of the appropriateness of these networks for AC and DC signal types. [ABSTRACT FROM AUTHOR]

Highlights: [•] A novel sacrificial material with low curing and removal temperatures. [•] A novel method to release piezoelectric freestanding microstructures directly on fabrics using only screen printing. [•] Cantilevers with a piezoelectric layer were achieved directly on fabrics. [•] Using printed cantilevers as the basis of the sensor, in the form of motion sensors, has been demonstrated. [•] The fabrication process would not affect the flexibility and breathability of the fabric using the interface layer which is only printed under the device. [ABSTRACT FROM AUTHOR]