Applications of statistical tools in various processing stages of textile production


Fiber Production

Measures of central tendency like process average gives an idea about average staple length of fibre produced in a continuous or batch wise process. Coefficient of variation (CV) of the process signifies about the process control. On the other hand, analysis of time series is helpful in estimating the future production based on the past records. Measures of dispersion such as standard deviation and CV are useful in comparing the performance of two or more fibre-producing units or processes. Significance tests can also be applied to investigate whether significant difference exists between the batches for means or standard
deviations. Analysis of variance can be applied for studying the effect of parameters of fibre production and methods of polymer dissolving.

Textile Testing of Fiber Yarn and Fabrics

Results analysis in textile testing without the applications of statistical tools will be meaningless. In other words every experiment in textile testing include the use of statistical tools like average calculation, computation of SD, CV and application of tests of significance (t-test, z-test and f-test) or analysis of variance (one way, two way or design of experiments). Populations can be very well studied by normal or binomial or Poisson’s distributions. Random sampling errors are used in studying about the population mean and SD at 95% and 99% level of confidence. Application geometric mean for finding out the overall flexural rigidity or Go has an important role in fabric selection for garment manufacture.

A special mention is made in determination of fibre length by bear sorter where all the measures of central tendency and dispersion (mean length, modal length quartile deviation, etc., in the form of frequency distribution) are computed to understand about the cotton sample under consideration for testing its potential in yarn manufacture. On the other hand ball sledge sorter uses weight distribution from which mean and SD are computed. In the case of cotton fibres, the development of cell wall thickening commonly referred as “Maturity” concept can be very well determined using normal distribution and confidence intervals. Several properties are tested for different packages produced from the same material or from the same frame by applying significance tests. Effect of instruments and variables for different types of samples can be
very well studied by using ANOVA. All the fabric properties tested on a single instrument or different instrument can be understood by using design of experiments. In one of the research applications, which include the testing of low stress mechanical properties for nearly 1000 fabrics are studied by ‘Principle Bi component analysis or Bi plot’. Measures of dispersion like coefficient of variation and percentage mean deviation are very much used in evenness measurement.

Yarn Production

There are several stages involved in the cotton yarn production. When fibres are mixed and processed through blow room, within and between lap variations are studied by computing mean, SD and CV lap rejection, and production control are studied by p and x charts. Average measure is used to find the hank of silver in carding, draw frame, combing and average hank of roving in roving frame and average count at ring frame. Generally the spinning mill use ‘average count’ as the count specification if it is producing 4–5 counts. On the other hand the weaving section uses ‘resultant count’ which is nothing but the harmonic mean of the counts produced. Control charts are extensively used in each and every process of yarn production (for example, the process control with respect to thin places, neps, etc.). Application of probability distributions like Poisson, Weibull and binomial for various problems in spinning is found very much advantageous to understand the end breakage concept. In ring spinning section several ring bobbins are collected and tested for CSP and difference between the bobbins and within the bobbins is studied using ‘range’ method. In cone winding section the process control can be checked either by using control chart for averages or chart for number defectives.

Fabric Production

Design of experiments such as latin square design or randomized block design can be used to identify the effect of different size ingredients on wrap breakages on different looms in fabric formation. Most of the suiting fabric constructions involve the use of double yarn which is nothing but the harmonic mean of different counts. Poisson’s and normal distribution can be applied for loom shed for warp breakages. Using statistical techniques the interference loss can also be studied in loom shed. Various weaving parameters such as loom speed, reed and pick can be correlated with corresponding fabric properties and are interpreted in terms of loom parameters. Control charts are used to study the control of process/product quality in fabric production also. For example, selection of defective cones in a pirn winding from a lot (fixed population) or in a production shift n p and p charts are used. The width of the cloth and its control can be understood by x and defectives per unit length and their control is understood by c charts. The testing process includes determination of average tensile strength (and single thread strength also) and the corresponding CV%.

Chemical processing and Garment Production

The scope of statistics is unlimited. For example the effect of n number washes (identical conditions) on m fabrics on a particular fabric property can be easily found by either tests of significance or analysis of variance. Similarly the effect of different detergents on fabric types can be investigated by two-way analysis of variance. Similarly different types of fabrics and the effect of sewing conditions can be studied by ANOVA.
In garment production the control of measurements and its distribution can be well understood by control and polar charts.

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A COMPRIHENSIVE DICTIONARY OF TEXTILE


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by  : Mason Brown

Textiles are fibres that are spun into yarn or made into fabric by weaving, knitting, braiding, and felting. The term is now applicable to natural and synthetic filaments, yarns, and threads as well as to the woven, knitted, felted, tufted, braided, bonded, knotted, and embroidered fabrics. The spinning and weaving were one of the first crafts that is believed to have been practiced as early as the New Stone Age. In ancient Egypt, the earliest textiles were woven from flax in India, Peru, and Cambodia, from cotton in the Southern European; from wool in China.

Textile also includes non-woven fabrics produced by mechanically or chemically bonding fibres. Computerised textile mill with multiple machines run continuously to produce textiles in the modern market. In a mill, the initial stage of processing fibre into fabric is almost entirely coordinated and controlled by computer. Computers are able to execute complex weaving and spinning jobs with great speed and accuracy. Most are equipped with monitoring sensors that will stop production if an error is detected.

The initial stage of textile manufacturing involves the production of the raw material either by farmers who raise cotton, sheep, silkworms, or flax or by chemists who produce fibre from various basic substances by chemical processes. The fibre is spun into yarn, which is then processed into fabric in a weaving or knitting mill. After dyeing and finishing, the woven material is ready for delivery either directly to a manufacturer of textile products to finally get stitched into clothes that we wear.

This book gives you an insight for terminology used in the textile industry. It should be helpful for everyone who is associated with garment, and textile industry.

To download this book please click on the following link.

http://www.4shared.com/office/SGs4M_TZce/2010_A_Comprehensive_Dictionar.html

The MAIN Shirt: A Textile-Integrated Magnetic Induction Sensor Array


By : Daniel Teichmann,  Andreas Kuhn, Steffen Leonhardt and Marian Walter

Abstract: A system is presented for long-term monitoring of respiration and pulse. It comprises four non-contact sensors based on magnetic eddy current induction that are textile-integrated into a shirt. The sensors are technically characterized by laboratory experiments that investigate the sensitivity and measuring depth, as well as the mutual interaction between adjacent pairs of sensors. The ability of the device to monitor respiration and pulse is demonstrated by measurements in healthy volunteers. The proposed system (called the MAIN (magnetic induction) Shirt) does not need electrodes or any other skin contact. It is wearable, unobtrusive and can easily be integrated into an individual’s daily routine. Therefore, the system appears to be a suitable option for long-term monitoring in a domestic environment or any other unsupervised telemonitoring scenario.

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The MAIN Shirt: A Textile-Integrated Magnetic Induction Sensor Array

CONTRIBUTION OF TEXTILE TECHNOLOGY TO THE DEVELOPMENT OF MODERN COMPRESSED BANDAGES


Bandage
Bandage (Photo credit: Wikipedia)

 

BY: – SVETLANA MILOSAVLJEVIC & PETAR SKUNDRIC

 

Although compression therapy is a key factor in the  successful treatment of some circulatory problems in lower limbs, this form of therapy includes some risks if used inappropriately. Based on deliberate application of pressure to a lower limb, using a variety of textile materials, elastic or rigid in order to produce a desired clinical effects,  modern compression therapy presents a good sample of successful penetration of textile technology into the phlebology field of medicine. However, although compression therapy has been in use for over 150 years, there exists a low awareness among practitioners and patients on the product usage, application techniques and benefit of appropriate selection of bandages for determined types of leg venous diseases. Also, not all manufacturers for compression textile materials seem to be conscious of end-users need. simultaneously, impressive developments in the field of elastic fibers and modern knitting and weaving technologies, offer chances for realization of completely new types of compressed bandages, capable of making an important contribution to the management of venous disease. In this review, starting from brief account of pathogenesis and the presentation of compression therapy principle, an account of the contribution of all sectors in the textile technology chain to a modern compression therapy is given.

 

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contribution of TT to the development of modern compression bandages

 

DIGITAL TECHNOLOGIES IN TEXTILE ART


by,

 Havva Halaceli

Cukurova University, Faculty of Fine Arts, Department of Textile Design,
Adana, Turkey

This is a digital age, dominated by information, communication and technology-based entertainment. This age is a result of rapid visual information-sharing. In this age, technology enables video sharing, saving every moment as visual data, and it is a result of rapid visual and information sharing. Today, artists use digital technologies as a means of expressing concepts. Woven textiles are also affected by the technological advances. Textiles have been essential for people from ancient times to now, for covering and protecting themselves from heat and cold. Weaving is a fine art form and a product of labor, including Coptic textiles and European tapestries; it can also utilize the speed, selection and color options of digital technologies that result from the mechanization and technological advances in the 20th century. Computerized Jacquard looms are one of the benefits of digital technologies that enable the weaving of complex imagery by allowing individual warp threads to be lifted.

Today, working with digital cameras, scanners and jacquard looms the textile artist becomes a designer and technology becomes a medium serving the artist’s creativity. In this study, the works of textile artists will be examined in view of time, technology and communication.
Keywords: Weaving, digital technology, jacquard loom

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Digital-Technologies-in-Textile-Art

OLEFIN FIBERS


Olefin fibers, also called polyolefin fibers, are defined as manufactured fibers in which the fiber-forming substance is a synthetic  polymer of at least 85 wt% ethylene, propylene, or other olefin units (1). Several olefin polymers are capable of forming fibers, but only polypropylene [9003-07-0] (PP) and, to a much lesser extent, polyethylene [9002-88-4] (PE) are of practical importance. Olefin polymers are hydrophobic and resistant to most solvents. These properties impart resistance to staining but cause the polymers to be essentially undyeable in an unmodified form.

The first commercial application of olefin fibers was for automobile seat covers in the late 1940s. These fibers, made from low density polyethylene (LDPE) by melt extrusion, were not very successful. They lacked dimensional stability, abrasion resistance, resilience, and light stability. The success of olefin fibers began when high density polyethylene (HDPE) was introduced in the late 1950s. Yarns made from this highly crystalline, linear polyethylene have higher tenacity than yarns made from the less crystalline. Markets were developed for HDPE fiber in marine rope where water resistance and buoyancy are important. However, the fibers also possess a low melting point, lack resilience, and have poor light stability. These traits caused the polyethylene fibers to have limited applications.

Isotactic polypropylene, based on the stereospecific polymerization catalysts discovered by Ziegler and Natta,was introduced commercially in the United States in 1957. Commercial polypropylene fibers followed in 1961. The first market of significance, contract carpet, was based on a three-ply, crimper-textured yarn. It competed favorably against wool and rayon–wool blends because of its lighter  weight, longer wear, and lower cost. In the mid-1960s, the discovery of improved light stabilizers led to the development of outdoor carpeting based on polypropylene.

In 1967, woven carpet backing based on a film warp and fine-filament fill was produced. In the early 1970s, a bulked-continuous-filament (BCF) yarn was introduced for woven, texturized upholstery. In the mid-1970s, further improvement in light stabilization of polypropylene led to a staple product for automotive interiors and nonwoven velours for floor and wall carpet tiles. In the early 1980s, polypropylene was introduced as a fine-filament staple for thermal bonded nonwovens.

The growth of polyolefin fibers continues. Advances in olefin polymerization provide a wide range of polymer properties to the fiber producer. Inroads into new markets are being made through improvements in stabilization, and new and improved methods of extrusion and production, including multicomponent extrusion and spunbonded and meltblown nonwovens.

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Olefin Fibers

ELECTRONIC TEXTILES: Wearable Computers, Reactive Fashion and Soft computation


Electronic textiles, also referred to as smart fabrics, are quite fashionable right now. Their close relationship with the field of computer wearable‘s gives us many diverging research directions and possible definitions. On one end of the spectrum, there are pragmatic applications such as military research into interactive camouflage or textiles that can heal wounded soldiers. On the other end of the spectrum, work is being done by artists and designers in the area of reactive clothes: “second skins” that can adapt to the environment and to the individual. Fashion, health, and telecommunication industries are also pursuing the vision of clothing that can express aspects of people’s personalities,social dynamics through the use and display of aggregate social information.

In my current production-based research, I develop enabling technology for electronic textiles based upon my theoretical evaluation of the historical and cultural modalities of textiles as they relate to future computational forms. My work involves the use of conductive yarns and fibers for power delivery, communication, and networking, as well as new materials for display that use electronic ink, nitinol, and thermochromic pigments. The textiles are created using traditional textile manufacturing techniques: spinning conductive yarns, weaving, knitting, embroidering, sewing, and printing with inks.

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textile-berzowska

Innovations in fibres and textile materials for sportswear


Fibre developments

The evolution of fibre developments has gone through the phases of conventional fibres, highly functional fibres and high-performance fibres. Polyester is the single most common fibre used for sportswear and active wear. Other fibres suitable for active wear are polyamide, polypropylene, acrylics and elastanes. Wool and cotton fibres are still finding applications in leisurewear. Synthetic fibres can either be modified during manufacture, e.g. by producing hollow fibres and fibres with irregular cross-section, or be optimally blended with natural fibres to improve their thermo-physiological and sensory properties. Synthetic fibres with improved UV resistance and having anti-microbial properties are also commercially available for use in sportswear.

Improved fibre spinning techniques in melt spinning, wet spinning, dry spinning as well as new techniques such as gel spinning, bi-component spinning and microfibre spinning, have all made it possible to produce fibres, yarns and fabrics with unique performance characteristics suitable for use in sportswear and sports goods. New technologies for producing microfibres have also contributed towards production of high-tech sportswear.

By using the conjugate spinning technique, many different types of sophisticated fibres with various functions have been commercially produced  which has resulted in fabrics having improved mechanical, physical, chemical and biological functions. The technique of producing sheath/core melt spun conjugate fibres has been commercially exploited for producing added-value fibres. Unitika produced the first heat-degenerating conjugate fibre with a core containing zirconium carbide (ZrC). Since ZrC absorbs sunlight (visible and near-infrared radiation) and emits far-infrared radiation, one feels warmer when one puts on a jacket made from such fibres. Other types of heat-generating fibres contain ceramic micro-particles.

High-performance fibres

Today, a wide range of high-performance fibres is commercially available for technical and industrial applications. These types of fibres are used in sports protective wear/equipment developed for impact protection and in textile reinforcement in sports products for different applications. Among the speciality fibres already established are the following:

Aramid fibres:

± p-aramid fibre to provide high strength and ballistics
± m-aramid fibre to provide flame and heat resistance.

Ultra-high tenacity polyethylene fibres (UHMWPE).

Gel spun, ultra-high molecular weight polyethylene fibres with extremely high specific strength and modulus, high chemical resistance and high abrasion resistance.

Polyphenylene sulphide fibres (PPS).

Crystalline thermoplastic fibre with mechanical properties similar to regular polyester fibre. Excellent heat and chemical resistance.

Polyetheretherketone fibres (PEEK).

Crystalline thermoplastic fibre with high resistance to heat and to a wide range of chemicals.

· Novoloid (cured phenol-aldehyde) fibres.

High flame resistance, non-melting with high resistance to acid, solvents, steam, chemicals and fuels. Good moisture regain and soft hand.

· PBO (p-phenylene-2,6-benzobisoxazole) fibres.

The strength and modulus of this fibre exceed those of any known fibres.

Highly functional fabrics

There has been a strong growth in the development and use of highly functional materials in sportswear and outdoor leisure clothing. The performance requirements of many such products demand the balance of widely different properties of drape, thermal insulation, barrier to liquids, antistatic, stretch, physiological comfort, etc. The research in this field over the past decade has led to the commercial development of a variety of new products for highly functional end-uses. By designing new processes for fabric preparation and finishing, and as a result of advances in technologies for the production and application of suitable polymeric membranes and surface finishes, it is now possible to combine the consumer requirements of aesthetics, design and function in sportswear for different end-use applications. The fabrics for active wear and sportswear are also specially constructed both in terms of the geometry, packing density and structure of the constituent fibres in yarns and in terms of the construction of the fabric in order to achieve the necessary dissipation of heat and moisture at high metabolic rates. Many smart double-knitted or double- woven fabrics have been developed for sportswear in such a way that their inner face, close to human skin, has optimal moisture wicking and sensory properties whereas the outer face of the fabric has optimal moisture dissipation behaviour.

In addition to the innovations in highly functional man-made fibre-based fabrics, advances have also been made in cotton and wool fabrics for sportswear. An example is the development of `Sportwool’ weatherproof technology, where the constituent fibre, yarn and fabric properties and the fabric finishes of `Sportwool’ are supposed to create a drier and cooler microclimate.

Since the introduction of Gore-Tex fabric in 1976, a variety of lightweight breathable highly functional fabrics have been developed worldwide. Highly functional fabrics are generally characterized as being waterproof/moisture permeable, sweat-absorbing and with high thermal insulation at low thickness values. These fabrics are now extensively used in making sportswear and sports shoes. One can say that these products are basically complex materials with diverse functions. In many of these products the requirements of comfort and fashion have successfully been integrated with segmentation in uses.

Important developments are envisaged in making multifunctional coated or laminated fabrics for different applications. For example, some new innovative functional textiles for protective clothing were recently introduced by W. Gore and Associates. Gore-Tex Airlock is a functional textile which was developed by Gore for the special needs of firefighters. The concept of this product is to eliminate the conventional, bulky, thermal insulation layer and substitute it by a protective air cushion. Dots consisting of foamed silicone are discontinuously applied to a fibre substrate and anchored within the microporous Gore-Tex membrane. They measure only a few millimetres in height, creating a defined air cushion between the adjacent flame-retardant face fabric and the inner lining. This laminated fabric is characterized by thermal insulation, breathability, perspiration transport, absorption and quick-dry properties.

Biomimetics and textiles

The structure and functions of natural biological materials are precise and well defined. The imitation of living systems, `biomimetics’, could make it possible in future to replicate the molecular design and morphology of natural biological materials since their structure and functions are related. Already in many laboratories around the world, R&D work is going on in the field of biomimetic chemistry and fabric formation. A typical example is the development of water- and soil-repellent fabrics produced by imitating the surface structure of a lotus leaf. Water rolls like mercury from the lotus leaf, whose surface is micro-
scopically rough and covered with a wax-like substance with low surface tension. When water is dropped on to the surface of a lotus leaf, air is trapped in the dents and forms a boundary with water.

Intelligent textiles

There have been some interesting developments taking place regarding intelligent textiles and interactive materials with great market potential in the sportswear sector. These materials readily interact with human/environmental conditions thereby creating changes in the material properties. For example, the phase-change materials and shape-memory polymers embedded in fabric layers will be able to interact with a human body and produce thermoregulatory control by affecting the microclimate between the clothing and the human skin. In addition to the two dimensions of functionality and aesthetics, if `intelligence’ can be embedded or integrated into clothing as a third dimension, it would lead to the realization of protective and safety clothing as a personalized wearable information infrastructure.

Reference: “Textiles in sports” by R.Shishoo

Cloth Finishing


Cloth Finishing

( Originally Published Early 1900’s )

Importance of cloth finishing.-Cloth finishing is one of the chief arts in the textile industry. The appearance of the goods is often of first concern, and the appearance of any fabric is largely due to the methods of finishing.

BLEACHING

Bleaching is one of the most usual and important among the finishing processes. It has for its object the whitening or decolorizing of the textile fiber to which it is applied. Fibers, as they come from the plant, from the back of the sheep, or from the cocoon, are usually somewhat colored or stained. Some of them, like tussah silk or Egyptian cotton, are highly colored. This natural coloring of the fiber may be undesirable in many fabrics; hence, bleaching is employed to clear the fiber of this color. Again, most fibers accumulate stains of various kinds during the early processes of manufacture as, for example, in the spinning and weaving. This discoloration cannot be entirely removed by simple washing; hence, the bleaching process is applied to clear the fabric. In like manner, when the calicoes or other prints come from the printers, the white background between the colored figures may be soiled, spotted, or otherwise discolored; again, a light bleach is applied, but not enough appreciably to injure the color in the figures.

Bleaching agents.-There are two classes of bleaching substances, oxygen and sulphurous acid. Under certain conditions oxygen destroys the coloring matters entirely. Sulphurous acid probably does no more than change the color to white, leaving the coloring substances still in the textile. An object once bleached white by oxygen is not likely to turn yellow or to change back to its original color; whereas textiles bleached in sulphurous acid quite frequently do change back again after a time, especially when in contact with certain chemicals such as alkalies or soaps.

Grassing.-The oldest bleaching method is that of “grassing,” still used to a certain extent in Europe for bleaching linens. The linen fabrics are laid on the grass or ground for weeks. The oxygen of the air and that given off by green plants slowly attacks and destroys the little yellow color particles in the flax fiber. Slowly the linen becomes whiter and whiter until finally it is fully bleached. The particular value of the grass bleach over all others is its slowness. This guarantees permanence. Furthermore, the “grassing” process is not likely to be carried on a bit further than necessary. The oxygen which attacks the coloring matter may ultimately attack the cellulose in the fiber and does do so in chemical bleacheries unless the fabric is removed at the proper time. A few moments’ delay, therefore, in a chemical bleachery means great damage to the cloth; whereas a few days either one way or the other in grass bleaching makes practically no difference. Cotton also was at one time bleached in this manner, but the more rapid chemical oxygen bleachers have entirely superseded grass bleaching for this textile.

Chemical bleaching.-The principal chemicals used in oxygen bleaching are chloride of lime, hydrogen peroxide, sodium peroxide, and potassium permanganate. All these substances are heavily charged with oxygen. In the bleaching process, this oxygen is set free, and this free oxygen attacks the coloring matters in unbleached goods. The bleaching powder of commerce is chloride of lime, the principal bleaching substance used for cotton and for all other vegetable fibers excepting jute. It is, however, entirely unsuitable for wool and silk. Hydrogen peroxide is the best bleaching substance of all. It may be used on any sort of fiber, for it attacks nothing but the coloring matter. It is frequently used in removing stains and also in bleaching hair. But for general textile bleaching purposes it is too expensive, and is hard to keep in concentrated form for even a short time. It is used extensively, however, in bleaching wool mousselines that are to be printed. Hydrogen peroxide produces a much better result than sulphurous acid, the common bleaching substance for wool. When cheaper means of producing peroxide are discovered, this chemical is bound to take front rank among the bleaching agents. Potassium permanganate is another oxygen-loaded chemical that is sometimes used in bleaching woolens. Sodium peroxide is a compound somewhat cheaper to produce than hydrogen peroxide, and contains a large amount of live, active oxygen. It is a rather new bleaching agent, but is already used to a certain extent on wool and silk, especially tussah silk.

Sulphur bleach.-Sulphurous acid bleach is applied in the form of either a gas or a liquid. The gas is produced by burning sulphur in the air. The fumes that arise from burning sulphur are sulphurous acid gas. The liquid is produced by saturating water with this gas. Sulphur bleach is used mainly for animal fibers (wool and silk) and jute. The most common method employs the gas rather than the liquid. Rooms called sulphur chambers are built out of brick especially for this purpose. The fabric or yarn is brought into this chamber and hung up damp in loose folds while sulphur is burned in pots on the floor. The rising fumes saturate the damp textiles, the dampness materially assisting, and the fibers gradually whiten. In large wool bleacheries the cloth is run through the sulphur chamber on rollers, bleaching on the way. The process is inexpensive and results in a beautiful white. Its tendency to make wool harsh is corrected by washing in soap and water. When the wool is mixed with cotton there is danger of the cotton’s being destroyed by the acid. The sulphur bleach is ordinarily used for wool and silk.

Chloride of lime.-In cotton bleaching, chloride of lime is the most common chemical used. Cotton is generally bleached in the piece or fabric form. The usual exceptions are sewing cotton, absorbent cotton, and jeweler’s cotton. The last two are bleached in the state of loose fibers. When the cotton comes from the looms it is still in the natural color, although somewhat altered by the sizing in the warp and by the dirt; grease, and dust accumulated in the machinery. The cloth is now said to be “in the gray.” It is, however, more of a dirty yellow than gray, and presents a soft, flabby, fuzzy, unattractive appearance. It is now ready for the bleaching process.

The bleaching process.-The cloth is first run through a washing machine to remove as much of the discoloration and dirt as possible. Next, most fabrics are either sheared or singed; that is, they are run through machines which either cut off or burn off the fuzziness that is always found on cloth direct from the loom. The shearing process is performed by a machine that works on the same principle as a lawn mower, cutting all loose ends and fibers very close to the body of the cloth. The singeing is done by very quickly passing the cloth over a line of gas jets, or over a red-hot plate, where the heat burns off the fuzz but has no time to burn the fabric itself. Recently, singeing has been successfully performed by electricity. Cloth is sometimes singed on both sides, sometimes on only one. The shearing and singeing processes leave the cloth apparently smooth.

As a rule, cotton cloths are then bleached. There are four common methods, or “bleachers” as they are called: “madder bleach,” “Turkey red bleach,” “market bleach,” and “rapid bleach.” Of these the madder bleach is the most thorough. The others differ from the madder bleach mainly in degree of thoroughness. Goods to be dyed in deep colors need less whitening; hence, they are given, for example, the Turkey red bleach. Goods to be dyed black need almost no bleaching; for these the rapid bleach is sufficient. The market bleach is really the rapid bleach with the addition of blueing and other substances to cover up defects in the process.

The bleaching industry.-Cotton bleaching is often conducted as a separate industry. In England this is quite the rule. The cloth is sent from the weaving concerns to the bleacheries to be bleached on commission or at so much a yard. Sometimes the products of the loom are purchased by converters who hire others to do all the finishing processes, including bleaching. Occasionally bleachers buy the cloth in the gray, bleach it, and again market it. In this country bleaching and dyeing works are usually associated, and both are frequently under the same management as the cotton mills. This joining together or integration of related industries is typical of American business organization, not only in the textile industries, but also in many other great businesses, such as steel production and meat packing.

How the bleacheries handle cotton goods.-Piece goods arrive at the bleacheries in bolts or rolls of an average length of fifty yards. Each of these is stamped with the owner’s name, the length of the bolt, and other necessary particulars. The ends of several hundred rolls are first stitched together to form one long sheet sometimes as much as twenty-five miles long.

Moistening and bowking.-When all is ready, the cloth is moistened, run through a six-to eight-inch ring to rumple it and form it into the shape of a rope, and in this form if is laid away in coils for several hours in bins to soften the sizing in the warp. Next, the cloth is turned into a covered tank called a kier, in which is a weak solution of caustic soda or milk of lime. The liquid is kept moving through the tank by means of pumps. Here the cloth is stirred for about eight or ten hours, a process which removes all fats and wax found in the cloth, such, for example, as the natu ral wax found around the cotton fibers. All of this must be thoroughly removed before bleaching if the cloth is to be made snow white. The mixture in the “kier” is called the “lime boil,” and this particular part of the process is called “bowking.” The process concludes with a thorough washing in pure, fresh water.

Brown sour.-The next step, known variously as the “brown sour,” “gray sour,” or “lime sour,” follows the washing. The cloth is passed into tanks of water containing sulphuric or hydrochloric acid, sometimes both. This souring process counteracts the action of any caustic soda or lime that may remain in the cotton fiber from the previous treatment. Here a knowledge of the chemistry of bleaching is absolutely essential. The proportion of acid in the “brown sour” must be just sufficient to destroy the alkali in the fiber. If not strong enough, the alkali will not all be destroyed and will continue to cause trouble throughout the entire life of the cloth. If too much acid is used, then not only will the alkali be destroyed, but the cotton fiber will be endangered as well. Much of the poor cotton cloth in the market owes its lack of strength to poor bleaching methods. Linen is more sensitive to these chemical changes than cotton; hence the difficulty of getting good chemically bleached linens. The acid or souring bath is followed by a washing in pure water.

Lye boil.-In the full madder bleach the cloth after the acid bath is usually passed into a second alkali bath containing hot lye and resin soap. This is called the “lye boil.” After three hours of boiling under pressure, with the alkali liquor forced through every part of the cloth by means of pumps, all of the fats and acids in the fiber have been ex tracted and changed into soapsuds. The invariable washing in pure water follows.

Chemicking.-The cloth is now ready to be transferred into the real bleaching bath, the chloride of lime solution, or “chemick,” as bleachers name it. Through this bath the cloth is passed back and forth, the liquid being forced through every part of it. After one or two hours this part of the process is completed. The cloth is removed and passed between heavy wooden rollers, which press out the excess of the chloride of lime solution. The cloth is then coiled or piled in bins so as to be exposed to the air. It is here that the real bleaching takes place. The chloride of lime absorbed in the fiber has a strong affinity for air and for water. Both are attracted, and in the chemical processes that follow a certain amount of oxygen is crowded out of the air and water, and this free, active oxygen attacks the coloring matters and destroys them. Now again the proportions must be scrupulously adjusted so that not too much or too little oxygen is produced. Too much would result in an oxidation or destruction not only of the color particles, but also of the cotton fiber itself.

White souring.-The chemicking or bleaching is followed by washing in pure water and afterward by treatment in a weak acid bath known as the “white sour.” In this bath all action of the chloride of lime is stopped. Then follows another most careful washing in water to remove every particle of acid, whereupon the bleaching process is ended. The cloth is opened up flat, spread out, beaten, stretched or tentered, and dried over hot rollers. It is now ready for dyeing, for printing, for mercerizing, or, if to remain in the white, for the final finishing processes of sizing and calendering. Dyeing, printing, and mercerizing have already been described; hence, we need only give our attention to the final finishing processes.

CLOTH DRESSING

Whether the cloth shall be made soft or stiff, dull or glossy, and so on, depends upon the finish applied and the materials used. Certain sizings fill up the spaces between the threads in the fabric, stiffen the fabric, and give it greater weight and body. Other sizing materials give stiffness without adding weight. Some give weight without stiffness. Some help to make the fabric glossy, others to give the cloth some special appearance in imitation of a different fiber. It would take a volume to give in detail an account of how these various effects are obtained. Such a description is not necessary here. A fair idea of the possibilities of cloth finishing can be obtained by a study of fabrics themselves, especially with the help of a small magnifying glass and with such tests as boiling and rubbing.

Dressing materials,-The materials used in cotton finishing or dressing include starches, glue, fats, casein, gelatin, gluten, minerals, and antiseptic substances. The starches give stiffness and weight; glue gives tenacity to the starches and other materials. Minerals, such as clay, are used to give weight. Fats give the qualities of softness and help make the fabric more elastic. Wax, stearin, and paraffin are frequently used to develop a high luster in the calendering or pressing processes. Antiseptic substances such as zinc chloride, salicylic acid, and zinc sulphate are added to prevent the starches and fats used in the dressing from molding or putrefying.

Starches.-The starchy substances commonly used include wheat flour, wheat starch, potato starch, rice starch, and cornstarch. Sometimes the starch is baked until brown before using. In this form it is called dextrin or British gum. Dextrin gives a softer dressing than any other starchy material. Wheat and corn starches produce the stiffest effects. Potato starch comes between the two extremes. Starch is sometimes treated for a couple of hours with caustic soda at about the freezing point. At the end of this time the excess of alkali is neutralized with acid. The result is a gum, called apparatine, which stiffens the cloth and does not wash out so easily as most other stiffening substances. Starch treated with acid produces glucose, and this is used largely as a weighting or loading material.

Fats.-Among the fats used are tallow, stearin, several different kinds of oils and waxes, and paraffin. These are sometimes added to the starches to reduce the stiffness of the fabrics. Glycerin and magnesium chloride are frequently added for the same reason. Fats may be added to waterproof the cloth, although waterproofing is usually accomplished by rubberizing; that is, by soaking the cloth in a solution of crude rubber or caoutchouc.

Minerals.-The minerals are added for various reasons. China clay increases the weight as do also salts of lime and baryta. Alum, acetate of lead, and sulphate of lead are sometimes used. Adding large proportions of borax, ammonium phosphate, salts of magnesia, and sodium tungstate makes the fabric fireproof.

How the dressing is applied.-The dressing material is usually applied as a liquid paste to the back of the cloth and then run over hot rolls or cylinders in order to dry the paste quickly. Sometimes it is applied lightly to the surface, sometimes it is pressed in deeply by means of rollers. When both sides are dressed, the fabric is passed into and through the dressing material. When the cloth is dry, the sizing or dressing process is complete. If merely a dull, hard finish is desired, nothing further is necessary except to stretch and smooth out the cloth, measure, bolt, and press it. But if any kind of polish is demanded, then the cloth must be calendered, pressed, mangled, or ironed.

CALENDERING

Calendering is accomplished by passing the cloth between large rolls, from two to six, under heavy pressure. In the rolls the dressing is smoothed out, and the hard, dull finish becomes soft and glossy in appearance. Heated rolls give a better gloss. When the rolls are made to turn over each other at different rates, there is a heavy friction or ironing effect on the cloth. For the highest glosses not only starch but also fats and waxes are used, and all are ironed into the cloth under heavy pressure and at as great heat as the cloth will stand. When calendered the fabrics are usually dampened first, just as clothes are dampened by the housewife before she irons them. The dampening in a cloth-finishing plant is done by a special machine that sprays the cloth very evenly as it passes through.

The beetle finish.-There are several special finishes possible through variations in the calendering process. Beetling is one of these methods. The cloth is passed into a machine over wooden rollers and beaten by wooden hammers operated by the machine. The beetle finish gives to cotton or linen an appearance almost like satin and is very beautiful.

Watered effects.-Moire or watered effects are produced by pressing some parts of the threads in a fabric down flat while leaving the other parts of the threads in their natural or round condition. The effect is usually that of an indistinct pattern. It is obtained in different ways, sometimes by running the cloth through the calender double, or again by running the single fabric between rollers especially engraved with moire designs. Only soft fabrics are suited to this finish; hence, no dressing except fats is used for moire goods.

Embossing.-Soft fabrics are sometimes stamped with patterns in the manner of embossing by means of engraved calender rolls. This process is called stamping.

Schreiner finish.-Another special finish, known as “Schreiner finish,” is applied in the calendering operation by passing the cloth between rolls covered with great numbers of finely engraved lines. The number often runs as high as six hundred to the inch. Under a pressure of 4,500 pounds these lines are pressed into the fabric. The result is that the round threads are pressed flat, but the lines break up the flat surfaces into little planes that reflect the light much better than an ordinary flat surface would. This peculiar light reflection gives the cloth the quality of a very high luster. Heating the rolls makes this luster more lasting. The effect is very beautiful. Mercerized cotton finished in the Schreiner finish rivals silk in appearance.

Most of the finishes spoken of so far, the result of dressing and calendering, are easily destroyed. Wear destroys any of them in time. Washing destroys most of them. But as long as they last they are highly important elements in the appearance of the fabrics.

OTHER FINISHING PROCESSES

Dressings applied to the various textiles.-Dressings are usually applied in much greater quantity to cotton than to any other textile. Linen comes second, and the principal dressing substance used in linens is starch. Glue, gelatin, dextrin, albumen, and water glass are applied under certain conditions and for certain effects in woolen goods. The common weighting materials added to woolens are short hairs or short wool fibers, sometimes called flocks. Flocks are the ends of fibers sheared off from the surface of wool or worsted cloth. Woolen cloths are padded or impregnated with these in the fulling mills, sometimes adding from one-fourth to three-fourths to the weight of the wool. Such finishing processes as beetling, mangling, moireing, and stamping are never applied to woolens. Silk usually has very little dressing applied to it in the finishing process, and that little generally consists of gelatin, gum arabic, or tragacanth. The other finishing processes are very much the same for silk as they are for cotton.

Lisle finish.-Several other finishes, or modifications of the finishes just described, are used in cotton goods when it is desired to show special effects. The lisle finish is given yarns that are to be used in the manufacture of hosiery and underwear. The true lisle finish is obtained by using combed, long-stapled, sea-island or Egyptian cotton. The yarns made from these fibers are rapidly but repeatedly run through gas flames until they are entirely free from any projecting fiber ends or fuzz. The result is a very smooth, glossy thread. Another kind of lisle finish is obtainable in a finished fabric, as, for example, in hosiery, by treating with a weak solution of sulphuric or hydrochloric acid and then drying before washing out the acid. The goods are afterward tumbled around in a machine that exposes them to the air and heats them to about 100 degrees Fahrenheit. After a time the loose ends and fuzzy fibers become brittle and break off in the tumbling given the goods. When the goods present the proper lisle finish, they are cooled off and washed in an alkaline bath which stops the action of the dry acid and neutralizes it. After thorough washing in clean water, they are dried and are ready for dyeing or any other finishing process. Sometimes the acids are added to the dye bath to cause more speedily the same effect in the appearance of the goods. Some dyes are regularly made up with the acid mixture.

Wool finishing.-The finishing processes for woolens and worsteds are much more laborious and complex than those employed for cottons. A greater variety of machinery is required, and there are more steps in the process. The finishing of wool goods is divided into two main parts: the first is called the “wet finishing,” which includes washing, soaping, steaming, carbonizing, and the use of liquids; the second is called “dry finishing” and includes napping, shearing, polishing, measuring, and putting up in rolls or bolts.

Preparation of wool fabrics.-Woolen or worsted cloth, as it comes from the weave rooms to the finishers, is first inspected for flaws, broken threads, and weak places, and wherever these are found, chalk marks are made to assist the burlers and menders in finding the places. To aid in the inspection, the cloth is generally “perched” or thrown over a roller and drawn down in single thickness by the inspector as fast as he can look it over. A good light is desirable. Inspectors with practice attain great proficiency in finding weak places or imperfections in the cloth. After the bad spots in the fabric are repaired the goods are tacked together; that is, the pieces are fastened together in pairs with the faces of the cloth turned towards each other. The tacking is simply a stitching along the edge, done either by hand or machine. The purpose of tacking is to protect the faces of the cloth from becoming damaged in any way by the heavy operations to follow or from becoming impregnated with any foreign substance difficult to remove, such as short hairs or flocks.

Fulling.-The next step is the fulling. All kinds of clearfinished worsted dress goods for ladies and practically all wool cloths for men’s wear except worsteds are fulled. This is the most characteristic process in the wool industry; no other textile goes through any process like it. The wool fibers, it will be recalled, are jointed and have scales that cause the fibers to cling together readily. This, we have learned, is called the felting quality. By beating a mass of wool fibers, a very hard, compact mass can be obtained, because the fibers creep into closer and closer contact with each other, holding fast because of the scales. Fulling makes use of this principle. Wool cloth is shrunken and made heavier and closer in structure and consequently stronger. Fulled cloth may also take many more kinds of finish than unfulled fabrics. The fulling process is performed in machines that apply pressure, moisture, and heat to the goods. The cloths are soaked in hot, soapy water, pressed, rolled, and tumbled; as a result, the woolen fabrics contract and become closer in texture throughout.

Flocking.-Short wool fibers or flocks are frequently felted into wool fabrics in the fulling operation. A layer of these short fibers is spread over the back of the cloth and matted down by moistening. In the fulling operation these fibers sink into the fabric and therefore help to give the fabric weight and closeness. That this process is not always well done is evidenced by the fact that the flocks in the backs of suitings often wear loose, drop down, and collect at the bottom of garments, especially at points where the lining and the suiting are sewed together. Flocks must from most standpoints be considered as an adulteration of wool although their presence really helps some fabrics, such as kerseys. All crevices are filled up and the fabric is made solid. If the felting has been done well, the flocks perform a good service in the cloth, but otherwise the flocks come out easily and are a decided nuisance to the wearer of the goods. Flocks made from wool waste such as shoddy, mungo, and extract, when applied on shoddy wool cloth are bound to come out. But flocks cut from new wool, when applied to new wool cloth, produce an excellent effect if not too largely used. Adding 25 per cent in weight to the cloth by flocking is not unreasonable, but doubling the weight of the original fabric would be unjustifiable adulteration. Flocking adds little if any to the strength of the cloth.

Speck dyeing.-After fulling, the cloth is washed very carefully, and is usually given a light dye to cover up spots or imperfections due to foreign matter that could not be taken out before. If not so dyed, all the little specks in the cloth have to be removed by hand, a process called speck dyeing or burr dyeing.

Carbonizing.-Carbonizing is usually performed before the wool is spun into yarn, but in some cases not until the cloth is woven. In this case it takes the place of speck dyeing. The process is the same for cloth as for loose wool. The vegetable matter is destroyed by soaking the cloth in weak acids and then heating in an oven.

Napping.-After washing, stretching, and drying, most goods are ready to receive the finish. In most cases this first involves raising a nap or fuzz evenly all over the surface, and for this purpose machines have been invented. The oldest of such machines use teasel or thistle burrs, whereas the later napping machines use little wire hooks. Some claim that the teasel burr has certain qualities for raising the wool nap that cannot be produced in any steel wire or spring hook or barb. The principle, however, is the same in all inventions for this purpose. The gigs or napping machines all stretch the cloth and then cause it to pass over many fine little hooks of teasel burrs or of steel wire which draw out a multitude of little ends of wool fiber all over the surface of the cloth. In some cases, the napping or gigging is performed on wet cloth; in others, the cloth is dry. Dry napping is in fact now the more common, although the wet methods are still employed for certain cloths and finishes.

The finish of wool cloth depends upon the degree o f napping and upon the variety of fiber. Meltons require only a little napping; kerseys, beavers, and doeskins, a very thorough one. Cloths that must wear exceedingly well must be napped as little as possible, since the process reduces the strength of the fabric. Cassimeres are given several kinds of finish, Saxony finish, for example, or velour finish. Other fabrics are each given their characteristic finish by slightly varying the amount of nap, or the treatment of the nap after it has been raised. Among such fabrics are cheviots, kerseys, meltons, beavers, chinchillas, outing flannels, doeskins, reversibles, thibets, satinets, blankets, and others.

Lustering.-After napping, such fabrics as kerseys, beavers, broadcloths, thibets, venetians, tricots, plushes, uniform cloths, and all worsteds, require another special operation known as steam lustering. Steam is forced through the cloth for about five minutes, followed by cold water. The steam brings out the luster which the cold water sets or fixes.

Stretching and clipping.-The dry finishing processes begin with stretching (or tentering) and then drying the cloth. Special machines accomplish this as well as all the other processes. The cloth now passes through a shearing machine which brushes the nap in the direction desired, afterward clipping it evenly over all the surfaces. The clippers operate like the revolving blades of a lawn mower. Goods that have not been napped are generally singed in much the same manner as cotton fabrics. Next, the sheared fabrics are brushed, and perhaps polished by means of pumice cloth or sandpaper, to make the cloth smooth and lustrous.

Final steps.-Finally the goods are pressed and thereby given a finished appearance. This is usually performed by means of heavy presses, either with dry heat or with steam. The most common present-day method of pressing cloth is by running it between heavy rollers heated by steam. Care must be taken not to get the rolls too hot or the wool will be damaged. The cloth is next inspected again, run through a measuring machine, doubled, rolled, and wrapped in paper, and packed into cases ready for the clothing manufacturer or the dry goods jobber and the retail store.

Worsted finishing.-Worsteds are not generally fulled as are woolens. After burling, worsteds are usually singed and then crabbed. The crabbing process sets the weave so that in the later operations it will not be obliterated. It consists in running the cloth tightly stretched over rollers through a trough containing hot water. After an hour or two of this the cloth is scoured and rinsed and then closely sheared. There are several varieties of worsted, each of which requires its own special finish or after-treatment. Innovations are constantly introduced to alter the appearance a little in one way or another. Among these are the fancy or yarn-dyed worsteds, serges, worsted dress goods, and worsted cheviots.

CURRENT AND FUTURE TECHNOLOGIES FOR WEARABLES AND E-TEXTILES


The technologies embedded in wearables influence the comfort, wearability and aesthetics. According to Tao (2005) (Figure 1) a typical system configuration of a wearables 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 wearables, a combination of aesthetic as well as functional pieces . Thus most common technological components used to develop fashionable wearables are: interfaces (connectors, wires, and antennas), microcontrollers, inputs (sensors), outputs (actuators), software, energy (batteries, solar panels), and materials (interactive or reactive materials, enhanced textiles).

Both classifications are overlapping each other, but for the purpose of this thesis they will be combined and all the concepts explained, with emphases on e-textiles. The project examples used in this section, supporting the theory are related to wearable textile technology already available on the market or projects currently being developed in research labs around the world showing promising results in becoming future technologies. The diversification of the project concepts goes from being very functional and practical towards more expressive and artistic.

Inputs

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.

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 wearables. They are usually designed from either multilayered woven circuits or polymer systems (Tao, 2005). At the dawn of ubiquitous computing environments, people will need to engage with many different devices with built-in microprocessors and sensors. 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. The devices of the future will have no faces(Saffer, 2007). They will implement more intuitive ways of interaction.

Origin Inputs
Person Voice, visuals, pressure, bend, motion, biometric data, proximity, orientation, displacement, smell, acceleration
Environment Temperature, light, sound, visuals, humidity, smoke, micro particles

Figure 1 – Suggestions types of inputs that a wearable system can collect

Voice recognition – Voice-controlled interfaces are currently most common on phones. However there are few drawbacks in the technology. It is difficult to create voice-controlled interfaces in public spaces, from both technical and design perspective, when the system should always listen for a command. In this case, incorrect processing of information is possible due to large influence of background noise. How will the system know to differentiate between a command and a background noise is a design challenge that yet needs to be answered. Furthermore, the current voice recognition technology has a problem distinguishing between different people’s voice and additionally, it requires more processing power then previous technologies. Leading researchers believe these obstacles will be overcome as technology advances, predicting that in a very near future we will interact with voice – controlled devices and environments.

Gesture recognition – As devices gain better awareness of the movement of the human body through technologies such as Global Positioning System (GPS) sensors and sudden – motion sensors (SMSs), gesture recognition as a way of human interaction with devices is becoming even more achievable. Indeed, there are devices such as mobile phones equipped with tilt motion sensors, so that users can, for example, “pour” media data from their phone to another device (Dachselt & Buchholz, 2009). Donneaud (2007) created a large textile interface for playing electronic music. Figure 2 illustrates the textile interface that is constructed of two conductive fabrics which are fixed on a frame each one weaved with conductive threads in a different direction.

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Figure 2: Textile XY: interface for playing music

When the performer presses any point of this textile, the two fabrics connect and the current electrical value is sent to the computer. This textile interface is flexibility and transparency, involving the whole body through choreographic movements in the musical interpretation, thus allowing the performer to explore the textile interface by look, touch and gesture.

Presence recognition – Person’s presence is another way of interaction with a system. Present- activated systems are one of the central research points for ambient intelligent environments. The main design and technical challenge here is what determines if the system should react to the presence of a person, how it should react and how fast this reaction should be after a change has been detected.

Outputs

There are a variety of output devices or materials which activate in wearables 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.

Senses Outputs
Visual LEDs, EL wires, displays, photochromic ink, thermocromic ink, E-ink
Sound Speakers, buzzers
Touch Shape memory wires, conductive yarns, conductive fabric, motors/actuators
Smell and Taste Scent capsules

Figure 3 – Overview of possible outputs that address specific senses

Communication Technology

For electronic components to truly become part of bigger interactive systems they need to be connected in order to exchange information. Wires, cables, antennas and connectors are most common physical components used to connect electronics together. Wired connections are secure and practical in many cases, but they can cause inflexibility and add to the weight of the system. On the other hand, wireless connections increase flexibility and the lightness of the system, but increase its complexity.

The advances in wireless technologies have played a significant role in the development of wearables and e-textiles, reducing the number of devices attached to a system, simplifying its construction as well as minimizing the size. According to Seymour(2009) some of the most common wireless communication and location based systems are: UMTS (Universal Mobil Telecommunication System), GPRS (General Packet Radio Service), GSM (Global System for Mobile Communication), GPS (Global Positioning System), Cell Triangulation, WIFI, Bluetooth, IR (Infrared) and PAN (Personal Area Network). These communication systems can be further subdivided to long- range or short range communications(Tao, 2005), if the transfer of information is between two or more users via the internet or a network protocol or between two or more wearable devices worn by a user, respectfully.

Long-range communications

The long-range communication technologies advanced during the mobile revolution. All portable devices such as mobile phones, PDAs, MP3 players use radio frequencies to enable communication. From the list above the following communication systems: UMTS, GPRS, GSM, GPS, cell triangulation, WIFI are long-range. GSM is the communication system currently most suitable for voice transmission, as well as for data and files transmission at 9.6 kbps. For transfer of pictures and video a third-generation (3G) wireless system is also available, with the capacity of 384 kbps. GPS and cell triangulation is suitable for navigation purposes. The variety of communication systems opens many possibilities for wearable devices and the exchange of information.

Short-range communications

Short-range communication for wearables is a research area that still needs to be developed. Some of the approaches considered for implementation in wearables are wiring, infrared, Bluetooth technology, WIFI, Personal Area Network (PAN) and Fabric Area Network (FAN). Even though they have some disadvantages, they show promising results as future technologies embedded in devices and textiles.

Embedding wires in garments is cumbersome and constrictive, and therefore not adequate. For infrared to be effective it requires direct lines of sight, which is not practical and difficult to implement on different devices worn on the body. Bluetooth technology is widely used, with an open wireless communication protocol which ensures connection between several devices within a short communication range (10 m), overcoming problems of synchronization. This technology is embedded in a range of products (such as smart phones, headsets, mouse, keyboards, printers and game consoles) and has many applications in situations where low-bandwidth communication is required. Bluetooth devices can interact independently of the user, as well as advertise services they provide, thus making this network more secure than other types, as more of the security, network address and permission configuration can be automated. This also provides an easier access to services for the users. WIFI (also called “wireless Ethernet”) uses the same radio frequency as the Bluetooth, but with higher power, resulting with a stronger connection. The users have the advantage to move around within a broad coverage area and still be connected to the network, through a variety of WIFI enabled devices such as laptops, smart phones, PDAs.

From a collaboration research project in 1996 between MIT Media Lab and IBM Almaden Research Center a new wireless technology emerged called the Personal Area Network (PAN) also referred to it as Body Area Network. The technology is considered the backbone of wearable technology, allowing exchange of digital information, power and control signals within the user’s personal space. PAN takes advantage of the natural electrical conductivity of the human body combined with a transmitter embedded with a microchip, to create an external electric field that passes an incredibly tiny current (1 billionth of an amp- 1 nanoamp) through the body, used to transmit data (IBM, 1996). As a comparison, the electrical field created by running a comb through hair is more than 1000 times greater than the current required for PAN technology to be functional. The technology is still being refined but researchers see great potential in PAN, as an effective and cost-efficient communication network. Passing of simple data between electronic devices carried by two people would be easier than ever, such as exchanging business cards via a handshake. This scenario as fascinating as it sounds also imposes many security issues, because touching a person with a PAN is like tapping a phone line (Tao, 2005).

In 2001 Hum proposed a wireless communication infrastructure to enable networking and sensing on clothing called the Fabric Area Network (FAN). The technology promises to solve some of the problems Bluetooth and GSM are facing, regarding the public concern of health hazards from the increased amount of emissions in the body from these sources of radiation. The new and innovative method, in which the technology architecture is designed, uses radio frequency (RF) fields for data communication and powering, restricted only to the surface of the clothing thus eliminating radiation into the body. More specifically, the technology uses multiple radio frequency identification FRID links, which have been used in the industry for years for tagging and tracking products. Even though the technology is being promoted as emission-save, low-cost and easy to maintain, it still has much more development it needs to undergo before such networking and sensing clothing can be considered for mass production.

The technologies described above such as GSM, GPS, WIFI and Bluetooth are already widely used as part of wearable devices. Since, they have been proven to be stable communicational systems and well developed; attempts have been made in the research community for their implementation in computational and smart textiles. However, these technologies were not initially designed for integration in clothing and accessories and thus researchers are modifying and perfecting these wireless networks to meet the requirements that currently established communication systems, cannot fulfill. For that reason, wireless networks such as PAN and FAN were originally designed and are still investigated.

Data management technologies and integrated circuits

The storing and processing of data in wearables is carried out in integrated circuits (IC), microprocessors or microcontroller. Integrated circuits are miniaturized electronic circuits which are mostly manufactured from silicon because of its superior semi conductive properties. However silicon is not flexible and therefore ICs are not very suitable for incorporating them on clothing. Developing ICs from conductive or semi-conductive polymeric Having the properties of a polymermaterials can be of great importance for wearable electronics since these materials are flexible, lightweight, and strong and of low production cost (Rossi, Capri, Lorussi, Scilingo, Tognetti, & Paradiso, 2005). Their down side is that they are not as efficient as silicon, and thus scientists are looking into developing electronics in the near future that will be a combination of both silicon and conductive polymers which will be complimenting each other.

Among the most advanced integrated circuits there are the microprocessors which are the heart of any normal computer. Also known as the CPUs (Central Processing Units), they present complete computation engines fabricated on single chips. The microprocessor performs many functions some of which are executing a stored set of instructions carrying out user defined tasks as well as carrying the ability to access external memory chips to both read and write data from and to the memory. From the architecture of the microprocessors, more specialized processing devices were developed, such as microcontrollers.

A microcontroller is a single-chip computer, which is embedded in many everyday products and therefore it is also called “embedded controller”. If a product has buttons and a digital display, most likely it also has a programmable microcontroller that provides a real-time response to events in the embedded system they are controlling. Such automatically controlled devices, often consumer products, are remote controls, cell phones, office machines, appliances, toys and many more.

Even though microcontrollers are “small computers”, they still have many things in common to desktop computers or large mainframe computers. All computers have a CPU which executes many different programs. In the case of microcontrollers the CPU executes a single program and thus they are known as “single purpose computers”. Also microcontrollers have a hard disk, a RAM (random-access memory) and inputs and outputs, which are all combined on a single microchip. Other characteristics common for a majority of microcontrollers, besides being embedded inside other devices dedicated to run specific single task programs, are that they come as low-power devices, small and at low cost, which is of great importance for wearable e-textiles. While some embedded systems are very sophisticated, many of those implemented in wearable e-textiles have minimal requirements for memory and program length, with no operating system and low software complexity. The actual processor used in the microcontrollers can vary widely, where ones choice when designing interactive applications depends on the context in which the embedded system will be used. The programs running on the microcontrollers can be stand-alone or can communicate with the software running on other external devices, preferably through a wireless network.

Energy management technologies

One of the biggest problems in wearable and integrated electronic technology is power and the quest for alternative energy sources is essential. Today batteries in the form of AA batteries or lithium batteries are the most common source of energy utilized for running embedded systems and processing of captured data through a microcontroller. However their life span is limited and designers of wearables will have to find new and improved solutions to acquire the needed energy, either making it long lasting or easy to recharge on the move. At the same time the energy source must become light and discreet, which currently is the heaviest part of wearables.

The need for alternative sources of power is rising as the demand for greater design freedom in creating light, flexible and reliable wearable e-textile is increasing. Researchers see a potential in an alternative source of power based on the miniaturization of fuel cell technology. The way fuel cells generate electrical power is similar to batteries, as they convert the chemical energy of a given type of fuel (e.g. hydrogen and oxygen) into electrical energy. They have longer lives than batteries of similar size since oxygen does not need to be stored, only hydrogen in metal hydrides (Larminie & Dicks, 2003). Before 2010 Toshiba is planning to launch the first commercial direct methanol fuel cell-based (DMFC) batteries for cell phones and laptops.

In the beginning of 2009 researchers from the University of Illinois claimed they have developed the smallest working fuel cell, with dimensions 3 mm x 3 mm x 1 mm and it is made from four layers: a water reservoir, a thin membrane, a chamber of metal hydride, and an assembly of electrodes (Heine, 2009). Scientists claim that with the capacity of 0.7 volts and a 0.1 milliamp current for about 30 hours the mini battery can be used to run simple electronics. Researches see a great potential in fuel cell technology as it is considered to be a clean, efficient and silent technology, nevertheless the main hurdles preventing commercial introduction is high cost, lack of durability, high system complexity and lack of fuel infrastructure (Bruijn, 2005).

Another interesting alternative energy source for intelligent clothing is to harvest the kinetic energy from the human movement or the fluctuations in body temperature. Even though this energy is very minimal to drive wearable technology and can only be measured in microwatts, it is still a research field that attracts attention. Some research has been done in piezoelectric materials, which creates charge when mechanically stressed, thus inserting them on shoes, walking power can be harnessed (Tao, 2005).

Other forms of power supply are utilizing photovoltaic cells which are gathering the energy of the sun, allowing a sustainable approach to wearable technology. There are many examples of products that are incorporating solar panels onto the surface of wearable e-textiles, using thin film printed on flexible surfaces such as plastics; however the efficiency of this alternative energy source still needs to be improved.

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 nanomaterial and piezoelectric materials.

By constantly improving and incorporating responsive materials in the development of light and flexible electronic components, conductive and semi-conductive materials, such as conductive polymers, conductive threads, yarns, coatings and inks, are receiving widespread attention. They are less dynamic then smart textiles but equally important in realizing fashionable, desirable, lightweight, soft and wireless computational textiles.

The following section gives an overview of conductive and responsive materials that are currently most used in wearable computational textiles.

Conductive fabrics and textiles are plated or woven with metallic elements such as silver, nickel, tin, copper, and aluminum. There are many different fabrics with various textures, looks and conductivity and few samples are illustrated in Figure 4 (left), those 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.

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Figure 4 : conductive fabrics (left) and Different types of conductive threads (Middle and right)

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. They contain metallic elements such as stainless steel or silver, with nylon or polyester as base fiber. Commercially available conductive threads usually vary in the resistance and the thickness of the thread. Figure 5 (middle and right) illustrates few commercially available threads. Since they are conductive when working with them, one has to take all the precautions as when using uncoated electric wire or a metallic surface without insulation. 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. Since wearable e–textiles require great flexibility, conductive inks are become more interesting for designers and developers in this area. Conductive inks contain powdered metals such as carbon, copper or silver mixed with traditional inks.

Shape memory alloys (SMA or muscle wire) are composed of two or more metals usually nickel and titanium, combination also known as Nitinol. These wires, usually of very small diameter, have the capacity to actuate when heated and to return to their original shape when cooled. Their capacity to flex or contract is up to 5% and it is a result of dynamic changes in their internal structure generated by an electric current. Some SMA wires can be “programmed” (heated at a transition temperature) into a particular shape for ex. zigzag or coiled. They can remember the form, to which they return when cooled. SMAs are used for triggering movement, have been woven in textiles or can make fabrics shrink or curl in wearable e-textiles applications. Long before SMAs were introduced to wearable e-textile projects, they have been used in many different areas, like electronics, robotics, medicine, automotive industry and appliances. SMAs are more and more becoming an interesting material for designers working on interdisciplinary projects across the fields of computation, technology, science, design and art. They explore how new ways of combining SMAs with computation can aid the design of responsive garments, objects and spaces and provide more meaningful interfaces.

Piezoelectric materials have the ability to generate electrical charge when exposed to mechanical stress (sound, vibration, force or motion). Piezoelectric materials exhibit reversible effect because they can produce electrical charge when subjected to stress and also they can generate stress when an electrical field is applied. Therefore the materials can be used both as sensors and actuators. Piezoelectric materials can serve as excellent environmental sensors, but the number of interesting applications in wearable e-textiles is even greater if they are coupled with other sensors, for ex. solar cells where they can be used to convert light to sound, motion or vibration.

Chromic materials are those that radiate, erase or just change the color based on the induction caused by external stimuli. They are also known as non- emissive “active materials” (Berzowska & Bromley, Soft computation through conductive materials , 2007). The classification of chromic materials depends on the stimuli affecting them. Some of the most know are photochromic and thermochromic materials. Most of the color changing phenomena (photochromism, thermochromism, electrochromism, piezochromism etc.) are reversible.

Photochromic (inks and dyes) are materials that react to light as an external stimulus. They are typically available in powdered crystals of ultraviolet (UV) sensitive pigments that need to be dissolved in an ink for application. Once the material is exposed to sunlight, blacklight or other UV source it will change from clear to colored state. When the UV source is removed they revert to their original state. They can be applied on various media, including textile, paper, plastic, wood and glass and can be used to create dynamic patterns that change in accordance to light variations in their surroundings.

Thermochromic inks are heat sensitive materials. They are made from various compounds that need to dissolve in the appropriate ink type for application. When exposed to a specific temperature they change from one color to another of from color to translucent. Thermochromic inks can be classified to three types, low – react to cold, body – react to body heat, touch and breath and high – react to hot liquids and air. They have the ability to infinitely shift color and with that create dynamic patterns on various substrates, including textiles.

Nanomaterials and microfibers have been the subject of enormous interest, over the past decades. They are materials fabricated on a molecular level. The technology is aimed at manipulating the structure of materials on atomic, molecular and nano16 level in a precise and controlled manner to create products or byproducts with specially engineered characteristics. Scientists use the prefix nano to denote a factor of 10-9 or one-billionth. One nanometer is one-billionth meter which is about 100,000 times smaller than the diameter of a single human hair (Qian & Hinestroza, 2004).

Many believe that the future development of many areas of our lives lie in nanotechnology, which fundamentals are based on the fact that properties of substances can change when their size is reduces to the nanometer range. The technology will be used in fabricating nanomachies, nanelectronics and other nanodevices to improve existing products and to create many new ones. Nanotechnology will also

have a great impact on textiles, being able to transform the molecular structure of the fibers and create fabrics that offer unsurpassed performance and comfort. The technology is likely to revolutionize wearable e-textiles, by not only developing very small and flexible electronic devices embedded in textile substrates, but it will go even further, ultimately having the electronic devices and system becoming the fabric itself. Researchers have already started to develop transistors in yarn form and to make conductive, carbon nanotube.

Refrance : E-textiles: The intersection of computation and traditional textiles (Interactive Sample Book by Marija Andonovska)