e-textiles are fabrics that feature electronics and interconnections woven into them, presenting physical flexibility and typical size that cannot be achieved with other existing electronic manufacturing techniques, explains Dr Anita Ajay Desai.
In the early 1990s Mark Weiser described the future of computing as disappearing from the consciousness of people. This means that computer systems will be unobtrusive and so easy to use that people can forget them and work with them without actively thinking of them. This so-called ubiquitous computing approach also implies the invisibility of hardware devices and continuous connectivity to information networks. Size reduction of electronics systems enables their integration into everyday objects and, at the same time, the distribution of computing capabilities to the surrounding environments.
Wearable electronics is still a fairly new field of research and as a result much of the terminology has still to gain widespread acceptance. The history of wearable electronics goes back to 1960s when Edward Thorp and Claude Shannon designed, implemented, and tested the first known wearable computer intended for roulette number prediction. The system, the size of a cigarette pack, consisted of a 12-transistor CPU, two micro switches as an input device for the toes, a loudspeaker as an output device, and a radio link. This application represents a special purpose system capable of doing only advanced specified tasks and also demonstrates the important feature of smart clothing applications, i.e., the usage of special UI devices. Its use, however, was forbidden in casinos at the time. One of the first public uses and, therefore, a starting point in the development of wearable electronics was Sutherland’s implementation of the Head-Mounted Display (HMD), which was utilised in virtual reality applications.
To realise this computing approach in practice, further development is needed such as in the miniaturisation of electronics as well as in new types of specialised UIs for ubiquitous applications. Hardware technologies having the strongest influence are the numerous emergent wireless communication technologies, improving processing and storage capacity of embedded platforms, new electronics packaging technologies, as well as high-quality display technologies.
The wearable electronics business powers from over $14 billion in 2014, to over $70 billion in 2024. The overall size of the smart textile market is estimated to be $289.5 million and expected to exceed $1,500 million by 2020.
Smart textiles are materials and structures of textiles, which can sense and react via an active control mechanism for the environmental conditions called stimuli. They are capable of showing significant change in their mechanical properties (such as shape, colour and stiffness), or their thermal, optical, or electromagnetic properties, in a handy manner in response to the stimuli. They are systems composed of different apparatuses and materials such as sensors, actuators, and electronic devices together.
Good examples are fabric and dyes that will change their colour with changes in PH, Clothes made of conductive polymers, which give light when they get electromagnetic signals, fabrics, which regulate the surface temperature of garments in order to achieve physiological comfort.
Smart textiles can be divided in to four types based on their functions:
- Passive smart materials are materials or systems, which only sense the environmental conditions or stimuli. They are just sensors. They show up what happened on them, such as changing colour, shape, thermal and electrical resistivity. These kinds of textile materials are more or less comparable with high functional and performance textiles. Micro fibres are very passive, waterproof; but at the same time permeable to water vapour.
- Active smart materials are materials and system that can both sense and respond to the external conditions or stimuli. Their prior functions are sensing and giving reaction to the stimuli. This shows they are both sensors as well as actuators to the environmental conditions.
- Very smart materials are materials and systems which can execute triple functions; First, they are sensors which can receive stimuli from the environment; Secondly they are able to give reaction based on the stimuli; Thirdly they can adapt and reshape themselves accordingly to the environmental condition. We can compare this system with the animal chameleon; Chameleon has a nature of taking the colour of the surrounding then react by changing the skin colour of itself to the colour of the surrounding and adapts to protect itself from the predators.
- Materials with even higher level of intelligence develop artificial intelligence to the computers.
These kinds of materials and systems are not fully achieved in the current investigation of human beings. This may be achieved from the coordination of those very smart (intelligent) materials and structures with advanced computer interface.
Wearable and electronics textiles: Electronic textiles are textile materials, fabrics, yarns and threads that incorporate with conductive fibres. Literatures call them smart fabrics, which are not only – wearable but also have local monitoring, computation as well as wireless communication capabilities.
Electronic textiles are an emerging interdisciplinary field of research that brings together specialists in information technology, micro systems, materials and textiles. They use kinds of conductive textiles, sensors, computational elements, and data and pwer distribution.
Sensing circuitry can be incorporated directly to washable and wearable clothing’s as well as built as yarns to collect information, monitor vital statistics and report them over a wireless channel for further processing. Every electronic-textile needs a power supply, electronic components and connection method to the textiles. Products such as the Nu Metrex Athletic garments that monitor heart rate, fabric keypads for controlling iPod, and textile heating products are examples. They can be used to create sensors, thermo-chromic displays, data transfer systems, antenna and heating elements.
As a consequence of the integration of wearable electronics or computing into clothing platforms, potentially with intelligent textile materials and non-electronic equipment, the outcome is smart clothes.
To highlight wearability and the clothing usage of wearable computing systems, they adopted the term smart clothing to refer to special-purpose wearable computers or electronics integrated in clothing. Smart clothing is composed of ordinary clothing with added intelligent structures. These structures can be formed with electronics, non-electronic equipment, intelligent textile materials, or their combinations. The purpose of smart clothing is to improve or augment the functionality of ordinary clothing in various ways such as providing better protection for their users or providing new ways to utilise their clothing. In order to complete the definition of smart clothing, we also require the systems to include facilities to sense their user or the environment and the capability to react to these measurements. Such reactions can be autonomous actions as with the control of electrical heating by human temperature measurements or provision of information to users.
Since the user is in close contact with wearable electronics, it is obvious that users’ acceptance is of fundamental importance. Some of the attributes affecting this are usefulness, easy and safe usage of the systems, social acceptance, and wear ability.
A crucial issue is how the electronics are sited and attached to soft clothing material. This integration of electronics has a direct bearing on the usage comfort of clothing.
Conductive fabrics: Current technologies used for conductive textiles include:
- Weaving of separate metal threads into the textile
- Printing/deposition of conductive polymers
- Printing metallic inks onto the surface
- Plasma deposition on the threads
- Electro less plating
Smart clothing design: The overall design of wearable electronics systems utilising a clothing platform or accessories is a demanding process since it requires multi-disciplinary group work. In addition to electronics and software engineers, representatives from human sciences, clothing and textile sciences, material science, and industrial design are needed to ensure functional designs.
Requirements for electronics design: The usage environment for smart clothing is mobile, which means that users move indoors, outdoors, and from one to the other. Regardless of the specific wearable electronics application environment, in comparison with office computing environments, the mobile environment poses greater challenges for electronics design. This is due to a variety of environmental factors, such as changing temperatures and humidity and means that the usage environment is more diversified than for desktop or laptop computers. Therefore, electronics need to be protected against adverse environmental conditions with suitable encasings that withstand a wide range of weather conditions such as cold and rain if needed.
Electrical power in smart clothes is utilised near the human body. Therefore, special attention needs to be paid to safety issues so that faults pose no danger to the user. Smart clothing applications are intended to be fully integrated systems, in which clothing and electronics are indistinguishable. At the moment, however, not all electronics withstand washing and so a good solution is to construct modular systems that can be utilised in different platforms and use components that can be easily replaced.
Modularity of the wearable electronics system is a key requirement when targeting the same concepts for several user groups. This requirement applies to the hardware part, which allows users to connect different functional modules to form an assembly and also to the software part, which needs to adjust to changing environments and hardware configurations. Even in the same user group, those users who have been able to adjust the functionality and UI according to their own preferences will adapt to new techniques more easily than others.
Requirements for clothing design: The reasons for wearing clothes are defined as protection, modesty and privacy, status, identification, self-adornment, and self-expression. Smart clothing applications are integrated into clothing. As a result, smart clothes also need to maintain the properties of clothing. Thus, clothing-like elements are utilised as often as possible in smart clothing application implementations. These include soft and flexible wiring, thin and flexible Printed Wiring Boards (PWBs), and clothing-like connector elements.
At present, smart clothing applications containing electronics need to be taken off for washing.
Suitable materials are available for electronics protection, but this will add to the cost of systems. In addition, these materials do not protect clothing or additional components from the mechanical strains they undergo in a washing machine.
Materials used: Depending upon the application, fabrics like cotton, acrylic, nylon, carbon fibers etc. are blended with various compounds to render them with both sensing and signal transmission functions. These are primarily used to measure strain, temperature, displacement, pressure, electric currents, magnetic fields, etc.
Wearable electronics applications: Wearable electronics applications can help people to survive in their every day life or workplaces by providing assistance or the tools for coping with a range of tasks. Numerous commercial products are available as technologies and dedicated devices. However, there are only a few examples of integrated smart clothing applications.
By contrast, there is a multitude of wearable electronics applications including much mobile computing equipment, portable music players, heart rate monitors, wrist-worn computers, and pedometers, all of which can be utilised while on the move.
These applications are typically used for hobbies and entertainment purposes.
The first reported commercial smart clothing applications were jackets that contained a MP3 player and a mobile phone. Later came clothes for snowboarding. The snowboard jacket contains an integrated fabric UI and mini disc (MD) player or a MP3 player. A wearable electrical heating jacket designed for mountaineers and a rescue vest containing an integrated communication system have also been introduced.
Examples of accessory-based applications are running shoes with intelligent cushioning and running shoes connected to a music player to support and guide the running performance with the aid of music.
In addition, a jacket containing pockets for a variety of electronics equipment has been launched. This jacket also provides the option of utilising a solar cell panel for battery charging and a patented Personal Area Network (PAN) solution for device connections.
Symbol Technologies has developed a commercial data collection system for applications in industry such as warehouse inventory and transportation control. This is designed to be worn on the wrist and equipped with a finger-worn bar code reader for ease of data collection.
Assisting applications for disabled: Several wearable applications for individuals suffering from physical, cognitive, or sensory impairment have been reported, from handheld applications (e.g. eye glasses) to prosthesis. Typical examples are guidance applications for the visually impaired such as VibraVest, which provides tactile user feedback about nearby objects. Another example is a haptic navigation guidance vest, which contains four by four arrays of tactile micro motors in the back of the vest to provide haptic directional information. Tactile feedback can also be utilised to assist the deaf.
Assisting applications for guiding, navigation and information access: Examples of wearable applications are the range of guiding, navigation, and information applications, which can help people in unfamiliar surroundings reach their desired destinations or provide information about shops, tourist attractions etc. For implementation of these applications, various positioning techniques are needed. For outdoor positioning, GPS is typically utilised.
The touring machine is a bulky backpack-wearable computer system combining mobile computing and augmented reality (AR) in a guiding application at a university campus area. Similar AR systems are also utilised for larger geographical areas. There is also a wearable guide designed for use on a campus area and capable of representing location-based multimedia information.
All the application examples of integrating GPS-based guidance systems in wearable computers utilise backpacks and also usually bulky HMDs to enable visibility of real world- and computer generated-assistance in the same visual field. Because of the inconvenience of these large and bulky GPS applications, we have also studied integrating GPS in clothing in inconspicuous ways. This application was designed for fishing and thus, required small and lightweight electronics.
Assisting collaborative and context-aware applications: Wearable electronics have been proposed as help in remote communication and establishing a collaborative community to enable conversation while performing other tasks. These collaboration tasks are particularly well suited for maintenance, repair, inspection, and construction tasks, in which expert advice can be needed. An example of such an application is the maintenance and repair of trains needed by railroad technicians. In this application, expertise at a distant location can provide help in fault diagnosis and repair, utilising digital data, audio, and images.
A step forward is the collaborative wearable systems that can also sense the environment remotely. This makes communication between the parties more natural because context-related information can be sensed in both places with no unintentional filtering. Wearable applications can also assist people with no network connections and help, for example, in the acquisition of new skills for carrying out complex tasks. These, however, are not collaborative applications.
A well-known application to improve overall quality of life is Steve Mann’s WearComp system. His system was inspired by still-life imaging and contains a camera-equipped wearable computer to allow users to observe their surroundings. This can also enhance their security, for example, by alerting the user of potential danger.
Assisting applications in workplace: Wearable electronics can also provide important benefits for people in a wide range of jobs. These include assistance in mobile office environments as well as in dangerous environments such as the military, the rescue services, or in space. However, most applications reported relate to manufacturing, maintenance, and inspection tasks such as aircraft maintenance, repair, and inspection. A wearable computer can provide additional information in diagnosis, troubleshooting, and repair as well as aid to memory for inspection lists, in which certain steps must be taken to ensure safety.
In addition, significant savings in time can be achieved when information is available through wearable systems. Wearable computers are also utilised to assure quality in food processing plants and to help in the documentation used by bridge inspectors by means of speech input assistance and the addition of automated notices to collected data. A wearable computer utilised with HMDs can provide vital information without interrupting the progress of the job by also enabling access to the relevant expertise.
Wearable computers have also been proposed for weapons maintenance as well as for training tasks for military personnel. Wearable applications in the field are challenging to design because of the unpredictable nature of the military context. Additional equipment should not encumber the user and hands free operation is clearly desirable. Fortunately, military clothing and other equipment offer considerable space for incorporating components. An HMD, a speech input, a navigation system, and a weapon system offer significant advantages such as hands free operation, information retrieval in the field, location information, and help in the preparation of field reports.
A clothing-like approach has been taken in the development of Sensate Liner, which detects bullet wounds in the torso using optical fibers. The system is constructed in a shirt. In addition to penetration occurrence, classification and localisation, it can measure heart and respiration rates and also movement. This system demonstrates techniques, which are also generally needed in wearable medical monitoring.
Firefighters can also experience similar life-threatening environments involving threats from radiation, high temperatures, and air shortages in air bottles. For stricter supervision in such working conditions and better communication between individual firefighters and the leader of the team, smart clothing systems should be able to withstand high temperatures. Wearable computers are also recommended for helping rescuers in disaster zones to provide assistance in such areas as data collection tasks and locating rescue team members.
Though manned space travel has a history of several decades, a microgravity environment leads to changes in physiological conditions with long-term missions being particularly risky. Important health issues in space concern radiation, loss of bone mineral density, behavioral changes caused by isolation, and changes in cardiovascular and pulmonary systems. In order to counter these risks to health, spacecraft and space stations are equipped with appropriate data measurement and collection devices. Space travel provides an ideal opportunity to utilise wearable systems to ensure long-term health monitoring before, during, and after journeys. An example of this is a sensor jacket, which can record Electrocardiogram (ECG), pulse, and tremor and also as well as produce muscular and cardiovascular loads with a hand dynamometer. Wearable computers also provide help in dangerous extra-vehicular or difficult tasks.
Assisting wellness technology applications: Physiological measurements in different forms are considered to be the key applications of wearable systems. Clothing is in close contact with the skin, providing the chance to perform measurements, which require skin contact. Clothes also offer privacy in personal health monitoring. Perhaps the most popularly known wearable electronics health monitoring systems are the heart rate monitors that are widely utilised in sports. These systems are usually based on a plastic-based sensor belt worn around the chest and a UI on the wrist. More clothing-like properties for wearable electronics systems are achieved by utilising ECF-based sensing elements. These are being studied in several research institutes and ECF electrodes are typically utilised to measure ECG, heart rate, and skin conductivity.
The earliest reported systems for physiological signal monitoring were usually simple and single- or two parameter-devices measuring, e.g., ECG, temperature, or accelerations of individuals. Later, prototypes for measuring typically skin temperature, heart rate, ECG, and accelerations were implemented. Nowadays the area of wellness technology has received considerable publicity for a number of reasons such as population aging and an increasing number of different life- style related diseases. Present physiological monitoring systems are typically based on wrist-worn devices or clothing-based systems. Various shirt, vest, suit, and accessory solutions contain textile electrodes to measure several physiological quantities and accelerations of individuals. In addition to data collection, wearable systems can be utilised for real-time feedback to enable continuous monitoring in every day life, thereby improving non-institutional care.
Entertainment and leisure-time applications: Various popular wearable electronics systems have been designed and implemented for musical entertainment. In addition to these, systems to help in creating networked music have also been designed and implemented. Items of clothing such as jackets, pants, or gloves become musical instruments when equipped with the necessary electronics and tactile sensors to create music and a network connection for shared listening and musical performance. A wearable system for creating every-day music based on different sensors in the user’s jacket produces music based on the user’s movements and environment Computer augmented art is also created utilising apparel such as footwear. With this system, a dancer wears special shoes equipped with sensors to measure different kinds of steps. According to the steps, the system generates music and computer graphics.
AR-based wearable electronics have been utilised for different games. Typical examples are games that have been changed from desktops to mobile environments in order to form a combination of computer-generated and real worlds. HMDs or PDAs are typically utilised as feedback devices. However, games for carrying fewer devices such as smart phones have also been designed. Another type of AR applications is a training help for billiards, which assists the player in executing strategic shots.
Previously smart textiles were presented as imaginary products and used in very limited areas. After scientific development smart textiles are presented as the future of the textile industry.
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