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[] Abdul Azeem/NTU/Fsd/Pk Electronic Textiles What is e-textiles? An electronic textile refers to a textile substrate that incorporates capabilities for sensing(biometric or external), communication (usually wireless), power transmission, andinterconnection technology to allow sensors or things such as information processing devices tobe networked together within a fabric. Electronic textiles allow little bits of computation to occuron the body. They usually contain conductive yarns that are either spun or twisted andincorporate some amount of conductive material (such as strands of silver or stainless steel) toenable electrical conductivity. Intelligent textiles , variously known as smart fabrics , electronic textiles, or e-textiles, haveattracted considerable attentions worldwide due to their potential to bring revolutionary impactson human life. An electronic textile is a fabric that can conduct electricity. If it is combined withelectronic components it can sense changes in its environment and respond by giving off light,sound or radio waves.. Electronic textiles (e-textiles) are fabrics that have electronics andinterconnections woven into them. Components and interconnections are a part of the fabric andthus are much less visible and, more importantly, not susceptible to becoming tangled together orsnagged by the surroundings. History The basic materials needed to construct e-textiles, conductive threads and fabrics have beenaround for over 1000 years. In particular, artisans have been wrapping fine metal foils, mostoften gold and silver, around fabric threads for centuries. Many of Queen Elizabeth I's gowns, forexample, are embroidered with gold-wrapped threads.At the end of the 19th century, as people developed and grew accustomed to electronicappliances, designers and engineers began to combine electricity with clothing and jewelrydeveloping a series of illuminated and motorized necklaces, hats, broaches and costumes .In 1968, the Museum of Contemporary Craft in New York City held a groundbreaking exhibitioncalled Body Covering that focused on the relationship between technology and apparel. Theshow featured astronauts’ space suits along with clothing that could inflate and deflate light up,and heat and cool itself. Particularly noteworthy in this collection was the work of Diana Dew, adesigner who created a line of electronic fashion, including electroluminescent party dresses andbelts that could sound alarm sirens.In the mid 1990s a team of MIT researchers led by Steve Mann, Thad Starner, and SandyPentland began to develop what they termed wearable computers. These devices consisted oftraditional computer hardware attached to and carried on the body. In response to technical,social, and design challenges faced by these researchers, another group at MIT, that includedMaggie Orth and Rehmi Post, began to explore how such devices might be more gracefullyintegrated into clothing and other soft substrates. Among other developments, this team exploredintegrating digital electronics with conductive fabrics and developed a method for embroideringelectronic circuits. [] Abdul Azeem/NTU/Fsd/Pk Categories: The field of e-textiles can be divided into two main categories: • E-textiles with classical electronic devices such as conductors, integrated circuits, LEDs,and conventional batteries embedded into garments. • E-textiles with electronics integrated directly into the textile substrates. This can includeeither passive electronics such as conductors and resistors or active components liketransistors, diodes, and solar cells.Most research and commercial e-textile projects are hybrids where electronic componentsembedded in the textile are connected to classical electronic devices or components. Someexamples are touch buttons that are constructed completely in textile forms by using conductingtextile weaves, which are then connected to devices such as music players or LEDs that aremounted on woven conducting fiber networks to form displays. Printed sensors for bothphysiological and environmental monitoring have been integrated into textiles including cotton,Gore-Tex, and neoprene. Manufacturing of e-Textiles A thread can be made to conduct electricity by either coating it with metals like copper or silver.It can also be made conductive by combining cotton or nylon fibers with metal fibers when it isspun. Current Technologies of e-Textiles The technologies embedded in wearable influence the comfort, wear ability and aesthetics.According to Tao (2005) a typical system configuration of a wearable includes several basicfunctions such as: interface, communication, data management, energy management andintegrated circuits.This classification is based on general purpose wearable computers. A similar classification ispresented by Seymour (2009) with focus on fashionable wearable, a combination of aesthetic aswell as functional pieces. Thus most common technological components used to developfashionable wearable are: interfaces (connectors, wires, and antennas), microcontrollers, inputs(sensors), outputs (actuators), software, energy (batteries, solar panels), and materials (interactiveor reactive materials, enhanced textiles). Inputs for e-Textiles: To obtain information for wearable devices components such as sensors are often used, forinstance, environmental sensors, antennas, global positioning system receivers, sound sensorsand cameras. Such sensors can be divided on active and passive (Langenhove & Hertleer, 2004)(Seymour, 2009). Active inputs are controlled by a user via a tactile or acoustic feedback system,which provides an intuitive interaction with the garment. Passive inputs collect biometric datafrom the human body as well as environmental data collected via wireless transmission system.The data is captured and further processed usually using a microprocessor. The table below [] Abdul Azeem/NTU/Fsd/Pk provides suggestions for the type of inputs wearable systems can collect from a person or theenvironment. Origin Input PersonVoice, visuals, pressure, bend, motion, biometric data,proximity, orientation, displacement, smell, accelerationEnvironmentTemperature, light, sound, visuals, humidity, smoke,micro particles Input Interfaces: The most common way for a user to interact with a device these days, involves the use ofbuttons, keyboards and screens, as they are proven to be easy to learn, implement and use withfew mistakes. Fabric- based interfaces using keyboards and buttons are most common forwearable. They are usually designed from either multilayered woven circuits or polymersystems. As wearable devices become more complex, a need for more complex interfaces arises.People want more options on their devices, they want everything, but they also want them withthe maximum of easy, freedom and comfort. This requires new ways of interaction, such as userengagement through voice, touch and gestures. Outputs: There are a variety of output devices or materials which activate in wearable as a result ofcomputation triggered by input data. Many outputs can stimulate any of the five the senses of thewearer or his audience. For example, shape memory alloy can change the silhouette of a fabricpresenting a visual experience for an audience and a tactile experience for the wearer. The tablebelow provides an overview of possible outputs to address specific senses. SensesOut put VisualLEDs, EL wires, displays, photo chromic ink, thermocromicink, E-inkSoundSpeakers, buzzersTouchShape memory wires, conductive yarns, conductive fabric,motors/actuatorsSmell, TasteScent capsules [] Abdul Azeem/NTU/Fsd/Pk Responsive materials: Responsive materials represent a new generation of fibers, fabrics and articles, which are able toreact in a predetermined way when exposed to stimuli, such as mechanical, electrical, chemical,thermal, magnetic and optical. They are reactive and dynamic and they have the ability to changecolor, shape and size in response to their environment. For many years researchers have devotedtheir work in developing responsive materials such as shape memory materials, chromicmaterials, micro and nano material and piezoelectric materials. The conductive and responsivematerials that are currently most used in wearable computational textiles are following: • Conductive fabrics and textiles are plated or woven with metallic elements such assilver, nickel, tin, copper, and aluminum these are: electronylon, electronylon nickel,clearmesh, softmesh, electrolycra and steelcloth. All these textiles show amazingelectrical properties, with low surface resistance15, which can be used for makingflexible and soft electrical circuits within garments or other products, pressure andposition-sensing systems. They are lightweight, flexible, durable, soft and washable(some) and can be sewn like traditional textiles, which makes them a great replacementfor wires in computational garments. • Conductive threads and yarns have a similar purpose to wires and that is to createconductive paths from one point to another. However, unlike wires they are flexible andcan be sewn, woven or embroidered onto textile, allowing for soft circuits to be created.Conductive threads and yarns offer alternative ways of connecting electronics on soft andflexible textiles medium as well offering traditional textile manufacturing techniques forcreating computational garments. [] Abdul Azeem/NTU/Fsd/Pk • Conductive coatings are used to convert traditional textiles into electrically conductivematerials. The coatings can be applied to different types of traditional fibers, yarns andfabrics, without changing their flexibility, density and handling. • Conductive ink is an ink that conducts electricity, providing new ways of printing ordrawing circuits. This special ink can be applied to textile and other substrates.Conductive inks contain powdered metals such as carbon, copper or silver mixed withtraditional inks. Other materials are • Shape memory alloys (SMA or muscle wire) • Piezoelectric materials • Chromic materials • Photochromic (inks and dyes) • Thermochromic inks • Nanomaterials and microfibers Electronic component integration Regardless of the conductive materials used to develop the electronic textile, the electroniccomponents and power supply must be either attached or embedded into the textile to create atruly interactive electronic textile. Some methods used are: • Soldering involves mounting the components directly onto the textiles surface. Thesolders are soft alloys of lead (Pb), tin (Sn), or sometimes silver (Ag) that is used to jointhe metallic electrical components within the textile. Soldering achieves good electricalcontact within the textile. • Bonding involves using conductive adhesives to embed components into textilesubstrates. Conductive adhesives can be developed according to the end use application.Non-toxic, highly conductive, highly durable, and moderately flexible conductiveadhesives can potentially be used to bond rigid components with flexible textilesubstrates. Components can also be stapled into conductive stitched circuits to createelectronic textile circuitry. This involves pressure forming a component to grip a sewnconductive trace within the textile substrate. • Joining involves attaching an electronic component's thread frame directly to a stitchedfabric circuit. Threads leading out of the electronic component can be stitched, punched,or woven through the substrate and can also be connected to other components. Impact of e-Textiles on recycling and disposal: The innovation trends of e-textiles if reviewed, and an overview of the material composition thescenarios are developed to estimate the magnitude of future e-textile waste streams. On that base,established disposal and recycling routes for e-waste and old textiles are assessed in regard totheir capabilities to process a blended feedstock of electronic and textile materials. The resultssuggest that recycling old e-textiles will be difficult because valuable materials are dispersed inlarge amounts of heterogeneous textile waste. Moreover, the electronic components can act as
