Pakistan Textile Journal

The state-of-art Smart Textiles
by
Mukesh Kumar Singh,

Government Central Textile Institute, Kanpur, India

The first smart material was developed by the thought of crease recovery in cellulosic fabrics in the dry and wet state in 1929. In the past twelve years, textile and clothing industry markets have changed due to more attention on smart textiles. Classic textile sectors have almost completely shifted from western world to Asian countries and western world has emphasized on smart textiles. Smart textiles have incorporated properties of responding to various stimuli and change their size & shape colour or behavior. Smart Textiles are one way of winning back lost position of textiles in world trade and are seen as the future of textiles.
Smart textiles
Smart textiles are defined as textiles that can sense and react to environmental conditions or stimuli, from mechanical, thermal, chemical, electrical, magnetic sources.
Three components may be present in smart materials- sensors, actuators and controlling units. The sensors provide a nerve system to detect signals. Some of the materials act only as sensors and some act as both sensors and actuators. Smart clothing is a combination of electronics and clothing textiles. New fibre and textile materials and miniaturized electronic components make it possible to create truly usable smart clothes. These intelligent clothes are worn like ordinary clothing providing help in various situations according to the designed application.
Textile products, which can act in a different manner than an average fabric and are mostly able to perform a special function, certainly count as Smart Textiles1. According to X. Ding and J. Hu, Smart Textiles are able to sense & respond to external stimuli in predetermined way.

Classification of smart textiles
According to functional activity smart textiles can be classified in three categories2.
Passive Smart textiles: The first generations of smart textiles, which can only sense the environmental conditions or stimuli, are called Passive Smart Textiles. A piece of clothing usually dries hanging, it requires a certain time to dry, so this means a passive drying. Optical fibre-embedded fabrics and conductive fabrics are the good examples of passive smart textiles.
Active Smart textiles: The second generation have both actuators and sensors. The actuators act upon the detected signal either directly or from a central control unit. Active Smart textiles are shape memory chameleonic water-resistant and vapour permeable (hydrophilic/non porous), heat storage, thermo regulated, vapor absorbing, heat evolving fabric and electrically heated suits.
Ultra Smart textiles: Very smart textiles are the third generation of smart textiles, which can sense, react and adopt themselves to environmental conditions or stimuli. A very smart or intelligent textile, essentially consists of a unit, which works like the brain, with cognition, reasoning and activating capacities. The production of very smart textiles is now a reality after a successful marriage of traditional textiles and clothing technology with other branches of science like material science, structural mechanics, sensor and actuator technology, advance processing technology, communication, artificial intelligence, biology etc.

Stages of incorporation Smartness in Textiles:
The different kinds of smartness can be incorporated in textile at three stages.

At fibre spinning level:
The fibre: Incorporating some active material in spinning dope or polymer chips prior to spinning can develop smartness. Thronging Institute of Textile and Plastic Research (Russia), modified the lyocell fibre by admixture of electrically conductive components during production to make it electrically conductive cellulosic fibre. These fibres can be used to prevent electrostatic charge generation in textiles for reducing surface resistance in the explosion proof material field in electrically heated textiles or as electromagnetic wave absorbers.
During yarn/fabric formation: The smartness of a textile can be improved by enhancing the smartness of yarn and by introducing active materials, sensors and activators during fabric formation.
At finishing stage: The smartness of textile material can be improved by applying some active finishes and synchronizing the electronic control units with each other.

Passive Smart Textiles
Ultraviolet Protective Clothing: The clothing which has an ability to absorb or reflect the harmful ultraviolet rays in terms of passive heat retention by numerous pores in textile product by means of bulked and micro-fibre constructions and use of UV absorbing chemicals. UV protective clothes can ascent the Ultraviolet Protection Factor (UPF) for wearer3.
Multi-layer composite yarns & textiles: The ultilayer composite yarns and textiles have other physical possibility for achieving wear comfort in terms of absorbing sweat released from the human skin surface by an internal sweat absorbent layer. Toyobo Co. Japan developed a cool & dry three layer composite yarn, which consists of a polyester filament yarn on the surface, a staple polyester yarn in the middle and a polyester filament yarn in the core. The finest components lying in the middle i.e. fine fibers offer greater porosity, which increases capillary action, conveying the absorbed sweat to the yarn surface. The coarse polyester filament yarn in the yarn interior has a Y-shaped cross section in order to increase moisture absorption capacity.
Plasma treated clothing4: Plasma treatment is a relatively new textile surface treatment technology. A German Company is offering diverse possibilities of finishing textiles, nonwovens, formed material and films from low energy plastic. The plasma treatment effects the wetting behavior of coating agents, adhesives and ageing resistant adhesion of applied plastics by increasing surface energy of the treated fabrics. The surface energy of mentioned materials is increased by plasma treatment with air in a continuous process. The plasma treated fabric results drastically improved adhesion of plastic applied. The plasma treatment modify the homopolar and insoluble thermoplastic plastics (e.g. Polyethylene PE, and Polypropylene PP) in a mass that can also be used for water based coating systems. Polar & insoluble thermoplastics e.g. Polyvinyl chloride PVC, Polyacrylate PA, Polystyrene PSD, and polypropylene PP can be modified in terms of adhesion.
Ceramic Coated Textile: The use of polymer materials for technical purposes in textiles is increasing constantly. The fluid ceramics is applied currently as ceramic coating for thermo ceramic construction and heat protection simultaneously. National Aeronautics and Space Administration NASA has reported the use of high performance coating system to protect material from high level of solar radiation and extreme cold conditions.
The base for fluid ceramics is formed by dispersion of a special acrylic resin in the tile form vaccumised ceramic silicon micro bodies (ceramic bubbles) of which energy is significantly throttled. The material composition of the dispersion coating (formulation for adhesives filling agents, pigments and the exclusive ceramic bubble state) can be tuned to each other in conjunction with bubble partial vacuum in such a way that new and more advantages characteristics features are produced. The following are particularly included for:

· The far-reaching effect of the technical and physical causes of heat loss (throttling of heat exchange by the ceramic bubble vacuum)
· Extreme sunlight reflection.
· Chemicals resistance of partially ceramic thin layer.
· Soiling tendency reduced due to rough coating surface.

Passive smart textiles & optical fibre sensors5 Optical fibre has offered both sensing and signal transmission facilities. Optical fibre sensors are devices for measuring strain, temperature, displacement, chemical concentration, acceleration, pressure, electric currents, magnetic fields and virtually any other material or environmental property.

The optical fibre sensors are able to sense the various battlefield hazards like chemical, biological and other toxic substances warfare threats. The polyurethane-diacetylene copolymer was chosen as the photochemical polymer for chemical sensor application. The passive cladding of the optic fibre was replaced with these sensitive materials, and the sensory system was integrated into textile structures. The pH sensitive sensors are developed and woven into the fabric of soldier's clothing6. A team at Georgia Institute of Technology developed a smart shirt embedded with sensors for electrocardiogram (ECG), heart rate , temperature, voice reading. Sensors collect all information from various parts of the wearer's body, then send to pager sized device attached to the waist portion of the shirt. The shirt was made by weaving a single-piece garment on a weaving machine to fit a 38-40 inch chest. The plastic optical fibre is spirally integrated into the structure during the fabric production process without any discontinuities at the armhole or seams by a novel modification in the weaving process. Copper core with polyethylene sheath and doped nylon fibres with inorganic particles are used for the electrical conducting. The plastic optical fibre was incorporated in an X-Y grid. A break in this grid would reveal the location of the wound. The amount of blood detected by the broken optic fibre would provide the information on severity of the wound. A Fabry-Perot interferometer was used for localised sensing of heart beat.

Conductive Fibre/ fabric: Many conductive fibres and yarns, e.g. metallic silk organza, stainless steel filament, copper, silver and gold or stainless steel wire-wrapped polymer filament, metal-clad aramid fibre, conductive polymer fibre, conductive polymer coating and special carbon fibre/fabric, have been applied to the manufacture of fabric sensors.

E.R Post and coworkers have engineered a few fabric structures that can sense pressure. The row and column fabric keyboards is a fabric switch matrix sewn from conducting and nonconducting fabric. The keyboard consist of two layers of highly conductive metallic organza with a resistance of about 100/m and nonconductive row separated by an insulating layer of nylon netting. When pressed at the right point, the two conducting layers make contact through spaces in nylon netting, and current flows from a row electrode to a column electrode. The keyboard can be repeatedly rolled up, crushed or washed without affecting its electrical properties. A firefly dress is manufactured using such structure to embellish the wearer's motion with an ever-changing display of light. A skirt was developed as one item from two layers of conducting organza (one supplying power and the other ground) separated by a layer of nylon netting. Light-emitting diodes (LED) with fuzzy conductive Velcro ends for electrical contacts are placed throughout the netting. When both ends of an LED brush against the power and ground planes, the circuit is complete and the LED lights.

Softswitch is being developed jointly by the Wronz and Paratech Ltd; Darlington. They have developed conductive textile connectivity and a polymer application process to create switching devices that retain the aesthetic and technical properties of conventional textiles. Printing, coating and embroidery can be used to manufacture these switches on a commercial scale7.A piezoresistive fabrics was used in the development of interactive gloves. These gloves make it possible to transform the movement of hand into an electrical signal, and to control the production of images with different colours. In the proposed device the electromechanical transduction properties of polypyrrole-coated Lycra fabric are exploited. The sensing system is fabricated by sewing coated Lycra fabric strips on the upper side of the fingers of a glove. The change in resistance caused by fabric strain due to finger flexion is read by simple electronic unit and sent to a computer through an A/D convertor.

Active Smart textiles
Some active smart fibres contain electric conductive materials, Phase Change Materials PCM, and graphite particles, which can conduct electricity. In this way the resistance of the fibre is changeable along with the change of the fibre temperature due to change of fibre volume. As the material warms, it expands and reduces conductivity between graphic particles. These materials can automatically regulate the on/off of the electricity and keep the temperature stable. PCM microcapsule was developed for US space travel agencies. In the production process, PCM is introduced into the textile fibre matrix in microcapsule form. These capsules prevent temperature variations by discontinuing temperature increases when the so-called phase change temperature is reached. The continuous energy fed from environment or form human body to PCM is stoared in it, increasing its thermal capacity. Inversely PCM materials give up their stored heat again as the environment cool down. Paraffins in particular find use for this function in the textile section.
The thermo catch heat insulation system developed by Mitsubishi Rayon with acrylic fibres contains in the fibre core fine ceramic particles which convert light into heat, and with an antimony / stannic oxide component in the fibre sheath. Such bicomponent yarn was used in Mobile-Thermo' Snow jacket with an integral heating system inside the garment which assured precise temperature control. That snow jacket was worn during 1998 Winter Olympics by members of Swiss team and 300 media persons in Nagano Japan.
Shape memory materials are materials that are stable at two or more temperature states. In these different temp erature states, they have the potential to assume different shapes, when their transformation temperatures have been reached. Shape memory polymers (SMP) are materials that have hard segments and soft segment e.g. polyurethane, polyester ether, styrene -butadiene copolymer etc. This is because the shape-memory materials exhibit some novel performances such as sensitivity, actuation, damping and adaptive response to external stimuli such as temperature, lighting, stress and field, which can be utilized in various ways in smart systems. Shape memory polymers were first developed in France and commercialised in Japan in 1984. Research activities have been proceeding in Japan, Europe, Korea, China, including Taiwan and the USA variety of polymers (about 20 types) have been developed with shape memory effects. SMPs are extensively used for textile finishing and laminated textiles. The first SMPs were polynorborene-based with a Tg range of 35ºC to 40ºC developed by French CdF Chinie Company and commercialised by Nippon Zeon Co. in Japan. Third kind of SMPs, introduced by Asahi Co. were styrene -butadiene based and had a Tg ranging from 60°C to 90°C.
Treating in a hydrolyzed fibroid keratin and collagen followed by subsequent drying, crimping, immersion in water and heat setting at high pressure in the wet state prepared shape memory silk yarn. Subsequent heating at 60°C the yarn becomes bulky and crimped, but it reverts to the untwisted and uncured state upon steaming. This elastic silk yarn can be used in various textile products like outer garments and knits.
Shape memory alloy wire and shape memory polymer films are already finding application in clothing. UKs Defence Clothing & Textiles Agency is designing garment with these materials to protect wearers against heat or cold. Cold protection in leisure wear is usually achieved by laminating a layer of insulation material, consequently, the wearer needs to select the appropriate garment for facing weather conditions. A garment having variable insulation would have greater versatility and this could be achieved by using a composite film of shape memory polymer as inter-liner.
The use of shape memory alloy in multiplayer fabric systems that change shape within a certain temperature range can be utilized to change the density between the individual layers. When temperature rises, an additional layer of insulating air is formed to enhance protection against heat8.
Chomeleonic textiles: S.Nanta9 from Toray Industries reported development of a temperature sensitive fabric with trade name SWAY in 1988 by introducing microcapsules, diameter 3-4 mm to enclose heat sensitive dyes, which are resin coated homogeneously over fabric surface. The microcapsule was made of glass and contained the dyestuff, the chromophore agent (electron acceptor) and colour- neutralizer (alcohol etc.) which reacted and exhibited colour / decolour according to the environmental temperature. SWAY was multicolor fabric, with basic 4 colours and combined 64 colours. SWAY can reversibly change colour at temperature greater than 5°C and is operable from - 40 to 80°C. The change of colour with temp of these fabrics is designed to match the application, e.g. for ski-wear 11-19°C, women's clothing 13-22°C and temperature shades 24-32°C.
T. Hongu and G. O Philips for Kanebo Ltd10. developed a fabric which can change colour from white to blue after irradiating with UV wavelength range 350-400nm. The spiropiran type organic compounds used for such photochromic material undergo photolyses and colour change by UV rays.
Due to low stability of Spiropiran Kanebo11 used a stable compound spiropiran as photo chromic material and a T- Shirt made of photochromic prompted fabric was introduced to the market in 1989.
In a Japanese Patent12 an endothermic fabric was used for colour change from green (below 15°C) to colourless (above 15°C). The fabric is capable of firmly changing colour within a specific temperature region, effectively absorbing near infrared rays only a colour change state, developing heat absorbing properties and providing a feeling of warmth. Hanks, Samuels and Gregory13 studied the dynamic colour change from tunable molecular and oligomeric devices. They developed an efficient, inexpensive method of attaching chromophores to the surface of polymers specially polyaniline, polypyrrole, polythiophene, and poly (ethylene-dioxythiophene). The researchers only studied the effect of electric field to a material either coated on to a fibre or containing to it .
Danial Cooper has designed a jacket that is useful for protecting the wearer from pollution. The front panels are made of nylon fabric embedded with nitrogen oxide. Sulfur dioxide and ozone monitors. When there is pollution, the fabric changes its colour from blue to orange14.
Heat storage textiles: The main object of heat storage or thermal regulatory textiles is to maintain the wearer in a state of thermophysiological comfort under the widest possible range of workloads and ambient conditions. Heat storage and thermoregulated textiles are novel comfort textiles that can absorb, redistribute and release heat by phase change in low melting point materials, according to change in surrounding temperature. National Aeronautics and Space Administration NASA planned to put the PCMs into gloves to keep pilot's hand warm. NASA developed textiles that aimed to improve the protection of instruments and astronauts against extreme fluctuations in temperature in space on the basis of heat absorbing and temperature regulating technology.
Vigo et.al.15 finished a polyester/cotton fabric with polyethylene glycol (PEG) as PCM and dimethyloldihdroxy-ethyleneurea (PMDHEU) to produce a thermally active fabric having 30-50 % add-on.
The Triangle Research & Development Corporation USA16 revealed in a patent in 1980s that treating solution-containing microcapsule could be treated on to the surface of woven, knitted and nonwoven fabrics. Lennox K P introduced 6-7% by wt PCMs microcapsule during wet-spun of PAN fibre17.
It is very difficult to produce the composite fibre by melt spinning only using PCMs as one component because melt viscosity of textile grade PCMs remains lower than required. They do not possess the required spinnability. After mixing PCMs with PEG of sufficient molecular weight, heat absorbing and temperature regulating fibre can be spun by core-sheath spinning. Watanabe18 has studied the melt-spun heat-storage and thermoregulated fibre containing Micro PCMs.

Ultra Smart Textiles
Very smart clothes are an effort to make electronic devices a genuine part of our daily life by embedding entire systems into clothing and accessories. This level of permanent and extensive data access will be revolutionary for the fields of communication, information, security and health care. These concepts are all made possible by a new textile technology called SOFTswitch19 that enables fabrics to function as electronic interfaces. SOFTswitch was exhibited to public in July 2000 as a result of collaboration between Wronz EuraLab Ltd, a textile research and development Organisation specialising in electronic fabrics and Peratech Ltd, a UK-based materials technology company. A joint venture company called SOFTswitch Ltd has now been established to manage and commercialise this technology. SOFTswitch Ltd is now working on development projects with broad spectrum of companies, and will market applications from intelligent industrial fabrics to wearable electronics.

SOFTswitch is made possible by combining lightweight conductive fabrics with a very thin layer of composite material having unique electronic properties. This composite material is an elasto-resistive


PCMs in the Textiles

composite or Quantum Tunneling Composite (QTC). This composite has an unique feature that in its normal state it is an insulator; however compressing or twisting it reduces the resistance until metal like connectivity is achieved. The mechanism of conduction in this composite is based on "Field-induced quantum tunneling". In the QTC Composites metallic particles are held in close proximity within a matrix, but never allowed to come into contact. When the fabrics containing the composite material are compressed or distorted the distance between the metallic particles decreases allowing electrons to tunnel between them and current to flow. In this way SOFTswitch fabrics exhibit a very broad change in Ohmic resistance, which is proportional to the pressure applied. With just a finger pressure the resistance can be reduced from billions of Ohms to less than one Ohm. Such behaviour knits itself to many application where proportional control of electronic devices is required.

Potential application for SOFTswitch technology is only limited by the imagination. Fabric switching devices can be designed to interface with any electronic device that is currently controlled or operated using switches, keypads, keyboards, buttons, knobs or sensors. This level of permanent and extensive data access will be revolutionary for the fields of communication, information, security and health care. C. Lauterbatch et. al.20 revealed the concept of "Smart Clothes powered by body heat" in his recent paper.
Very smart textiles are developing with or without the help of SOFTswitch technology. The applications include spacesuits, Musical Jackets, Smart Clothing (Remina Smart Suit), I-wear, Datawear, Wearable computers, Intelligent Interior Surfaces, Flexible Computing Interfaces, Advanced Learning Products and Clinical Pressure Monitoring.

Spacesuits: The earliest developed Appolo spacesuits contained an inner layer of nylon fabric with network of thin walled plastic tubing which circulated cooling water around the astronaut to prevent overheating. This inner layer was comfort layer of lightweight nylon with fabric ventilation ducts, then a three-layer system formed the pressure garment. Next followed five layers of aluminized Mylar for heat protection, mixed with four spacing layers of Dacron. These were covered with a non-flammable and abrasion-protective layer of Teflon-coated beta cloth. The outer layer was Teflan communication cloth. The backpack unit contained a life support system providing oxygen, waters and radio communications21.
Musical Jacket turns an ordinary jacket into a wearable musical instrument and allows the wearer to play notes, chords, rhythms and accompaniment using any instrument available in musical scheme. It integrates fabric keypad, a sequencer, synthesizer, amplifying speakers, conductive organza and batteries to power these subsystems.

The smart clothing projects started in different universities of Japan and USA in 1998 and first Remina Smart Suit came in European Market in September, 2001 commercially based on Global System for Mobile GSM Communications Technology. The smart suit consists global mobile system for communication, functional architecture for navigation, and electrically heated fabric panels for heating. The sensor system consists of a heart rate sensor, three positions and movement sensors, 10 temperature sensors, an electric conductivity sensors and two impair detecting sensors. The implementation and synchronization requires a user interface (UI), a central processing unit (CPU) and a power source. Each main module, excluding the sensors and the UI is set into the supporting vest. This smart suit allows easy, fast and cost-efficient group communication. A cellular telephone, loudspeaker and microphone are incorporated in the belt. By pulling a tag on this belt, hand, piece communication can be achieved by groups of people engaging in snow war22.

Intelligent wear (I-Wear): Starlab, a Belgian private company is developing intelligent clothing and first prototype of its intelligent clothes was presented in June 2000.

I-clothes are made of six technical layers, each with a specific function. The team of Starlab developed a wireless communication system and Fabric Area Network to permit networking of sensors and data on clothing. This wireless network allows communication between the various layers, without danger of radiation to the body. The network is integrated in a natural and flexible manner into the fabrics.

Datawear
A British company TCAS, the first inventor of Datawear have spent many years developing this system. Datawear incorporates sensors at each of the body joints plotting the position on a graph, which is calculated on a computer. The sensors are made from conductive elastama. Datawear cloths consist a bunch of magnetic position sensors the TCAS system measures the angle of each of the joints to determine absolute position of each of the limbs. It has been designed for comfort and ease. The sensors can be placed to specification for individual applications. The Datawear body unit consists of jacket, trousers and gloves that are circuited or wired electronically for interaction with computer. The application of Datawear to track position of limbs in computer data, medical imaging, measurement, ergonomics biomechanics, robotics and animation. The whole body can be monitored by Datawear, which has a particular relevance in the fields of sports injuries and biomechanics.

Smart clothes: - F.A.C Fashion & Design Germany developed smart clothes have some excellent characteristics like rounded organically lines, new pocket shapes, rounded zippers, smart reflective logo, natural soft lettering, and top stitching integrated in solar cell. These small clothes are wearable electronics as integral part of the garment, mobile, recorder and global positioning system GPS systems.
Sports Jacket:- Philips Research Laboratories has developed material with conductivity that changes in a predictable way as it is stretched. They made a sport jacket that can sense the arm movements of the wearer. Sport jacket could be used to monitor and assist people when playing sports23.
Intelligent bra: - Wallace et.al at University of Wollon, Australia are developing a smart bra that will change its properties in response to breast movement. This bra will provide better support to active women when they will be in action. Smart bra will tighten and loosen its straps, or stiffen and relax its cups to restrict breast motion, preventing breast pain and sag. The conductive polymer coated fabrics will be used in the manufacture of Smart bra. The fabrics can alter their elasticity in response to information about how much strain they are under. The smart bra will be capable of instantly tightening and loosening its straps or stiffen cups when it detects excess movement.


Wearable Computer

Wearable computer
Boeing Computer Services, Honeywell Ind. Virtual Vision, Carnegic Melloon University and some other research organisations are developing a wearable computer system that is better powered computer system worn on the user's body (on a belt, backpack or vest). Wearable computer is designed for mobile and predominately hands-free operations, head mounted displays and speech input.

Conclusion
People are already carrying around more and more electronic products; mobile phones, laptops, and more one the way. It makes perfect sense to actually start integrating smart products into clothes.
Smart clothing is a combination of electronics and clothing textiles. New fibre and textile materials and miniaturized electronic components make it possible to create truly usable smart clothes. These intelligent clothes are worn like ordinary clothing providing help in various situations according to the designed application. Though lot of new products have come but still there is vast scope to utilize developed smart technologies or evolve new technologies for Smart applications

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