Electronic Textiles | Current Technologies of E-Textiles | Manufacturing Process of E-Textiles

 Electronic Textiles
Anam Saleem
Department of Textile Engineering
University of Managment and Technology, Lahore, Pakistan
Email: 111811017@umt.edu.pk

What is e-textiles?
Intelligent textiles, variously known as smart fabrics, electronic textiles, or e-textiles, have attracted considerable attentions worldwide due to their potential to bring revolutionary impacts on human life. An electronic textile is a fabric that can conduct electricity. If it is combined with electronic 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 and interconnections woven into them. Components and interconnections are a part of the fabric and thus are much less visible and, more importantly, not susceptible to becoming tangled together or snagged by the surroundings. An electronic textile refers to a textile substrate that incorporates capabilities for sensing (biometric or external), communication (usually wireless), power transmission, and interconnection technology to allow sensors or things such as information processing devices to be networked together within a fabric. Electronic textiles allow little bits of computation to occur on the body. They usually contain conductive yarns that are either spun or twisted and incorporate some amount of conductive material (such as strands of silver or stainless steel) to enable electrical conductivity.

The basic materials needed to construct e-textiles, conductive threads and fabrics have been around for over 1000 years. In particular, artisans have been wrapping fine metal foils, most often gold and silver, around fabric threads for centuries. Many of Queen Elizabeth I's gowns, for example, are embroidered with gold-wrapped threads.

At the end of the 19th century, as people developed and grew accustomed to electronic appliances, designers and engineers began to combine electricity with clothing and jewelry developing 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 exhibition called Body Covering that focused on the relationship between technology and apparel. The show 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, a designer who created a line of electronic fashion, including electroluminescent party dresses and belts that could sound alarm sirens.

In the mid 1990s a team of MIT researchers led by Steve Mann, Thad Starner, and Sandy Pentland began to develop what they termed wearable computers. These devices consisted of traditional 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 included Maggie Orth and Rehmi Post, began to explore how such devices might be more gracefully integrated into clothing and other soft substrates. Among other developments, this team explored integrating digital electronics with conductive fabrics and developed a method for embroidering electronic circuits.

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 include either passive electronics such as conductors and resistors or active components like transistors, diodes, and solar cells.
Most research and commercial e-textile projects are hybrids where electronic components embedded in the textile are connected to classical electronic devices or components. Some examples are touch buttons that are constructed completely in textile forms by using conducting textile weaves, which are then connected to devices such as music players or LEDs that are mounted on woven conducting fiber networks to form displays. Printed sensors for both physiological 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 is spun.

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 basic functions such as: interface, communication, data management, energy management and integrated circuits.

This classification is based on general purpose wearable computers. A similar classification is presented by Seymour (2009) with focus on fashionable wearable, a combination of aesthetic as well as functional pieces. Thus most common technological components used to develop fashionable wearable are: interfaces (connectors, wires, and antennas), microcontrollers, inputs (sensors), outputs (actuators), software, energy (batteries, solar panels), and materials (interactive or reactive materials, enhanced textiles).

Inputs for e-Textiles:
To obtain information for wearable devices components such as sensors are often used, for instance, environmental sensors, antennas, global positioning system receivers, sound sensors and 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 data from 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 provides suggestions for the type of inputs wearable systems can collect from a person or the environment.
Voice, visuals, pressure, bend, motion, biometric data, proximity, orientation, displacement, smell, acceleration
Temperature, 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 of buttons, keyboards and screens, as they are proven to be easy to learn, implement and use with few mistakes. Fabric- based interfaces using keyboards and buttons are most common for wearable. They are usually designed from either multilayered woven circuits or polymer systems. 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 with the maximum of easy, freedom and comfort. This requires new ways of interaction, such as user engagement through voice, touch and gestures.

There are a variety of output devices or materials which activate in wearable as a result of computation triggered by input data. Many outputs can stimulate any of the five the senses of the wearer or his audience. For example, shape memory alloy can change the silhouette of a fabric presenting a visual experience for an audience and a tactile experience for the wearer. The table below provides an overview of possible outputs to address specific senses.
Out put
LEDs, EL wires, displays, photo chromic ink, thermocromic ink, E-ink

Speakers, buzzers
Shape memory wires, conductive yarns, conductive fabric, motors/actuators
Smell, Taste
Scent capsules

Responsive materials:
Responsive materials represent a new generation of fibers, fabrics and articles, which are able to react 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 change color, shape and size in response to their environment. For many years researchers have devoted their work in developing responsive materials such as shape memory materials, chromic materials, micro and nano material and piezoelectric materials. The conductive and responsive materials that are currently most used in wearable computational textiles are following:
  • Conductive fabrics and textiles are plated or woven with metallic elements such as silver, nickel, tin, copper, and aluminum these are: electronylon, electronylon nickel, clearmesh, softmesh, electrolycra and steelcloth. All these textiles show amazing electrical properties, with low surface resistance15, which can be used for making flexible and soft electrical circuits within garments or other products, pressure and position-sensing systems. They are lightweight, flexible, durable, soft and washable (some) and can be sewn like traditional textiles, which makes them a great replacement for wires in computational garments.

  • Conductive threads and yarns have a similar purpose to wires and that is to create conductive paths from one point to another. However, unlike wires they are flexible and can 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 and flexible textiles medium as well offering traditional textile manufacturing techniques for creating computational garments. 

  • Conductive coatings are used to convert traditional textiles into electrically conductive materials. The coatings can be applied to different types of traditional fibers, yarns and fabrics, without changing their flexibility, density and handling.
  • Conductive ink is an ink that conducts electricity, providing new ways of printing or drawing circuits. This special ink can be applied to textile and other substrates. Conductive inks contain powdered metals such as carbon, copper or silver mixed with traditional 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 electronic components and power supply must be either attached or embedded into the textile to create a truly interactive electronic textile. Some methods used are:
  • Soldering involves mounting the components directly onto the textiles surface. The solders are soft alloys of lead (Pb), tin (Sn), or sometimes silver (Ag) that is used to join the metallic electrical components within the textile. Soldering achieves good electrical contact within the textile.
  • Bonding involves using conductive adhesives to embed components into textile substrates. Conductive adhesives can be developed according to the end use application. Non-toxic, highly conductive, highly durable, and moderately flexible conductive adhesives can potentially be used to bond rigid components with flexible textile substrates. Components can also be stapled into conductive stitched circuits to create electronic textile circuitry. This involves pressure forming a component to grip a sewn conductive trace within the textile substrate.
  • Joining involves attaching an electronic component's thread frame directly to a stitched fabric 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 the scenarios 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 to their capabilities to process a blended feedstock of electronic and textile materials. The results suggest that recycling old e-textiles will be difficult because valuable materials are dispersed in large amounts of heterogeneous textile waste. Moreover, the electronic components can act as contaminants in the recycling of textile materials. So technology developers and product designers should implement waste preventative measures at the early phases in the development process of the emerging technology.

Advantages of e-Textiles:

  • Flexible
  • No wires to snag environment
  • Large surface area for sensing
  • Invisible to others
  • Cheap manufacturing 

About the Editor-in-Chief:

Mazharul Islam Kiron is a textile consultant and researcher on online business promotion. He is working with one European textile machinery company as a country agent. He is also a contributor of Wikipedia.

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