State of the art in Smart Textiles and Interactive Fabrics
During the last ten years the traditional textile industry, that during the decades has
favoured quality, has changed its strategy to support the innovation and the creation of
new products and functionalities. This inversion of situation has allowed the
consolidation of the emergence of two areas: “Technical Textiles” and “Smart Textiles
and Interactive Fabrics (SFIT)”.
The present document aims to relate the several major advances and related products
which appear with the blossoming of intelligent textiles.
I. Introduction
Intelligent textiles represent the next generation of fibres, fabrics and articles produced
from them [1]. They can be described as textile materials that think for themselves, for
example through the incorporation of electronic devices or smart materials. Many
intelligent textiles already feature in advanced types of clothing, principally for
protection and safety and for added fashion or convenience.
One of the main reasons for the rapid development of intelligent textiles is the important
investment make by the military industry. This is because they are used in different
projects such as extreme winter condition jackets or uniforms that change colour so as
to improve camouflage effects. Nowadays, the military industry has become aware of
the advantage of sharing knowledge with the various industrial sectors, because with
joint collaboration far better results can be obtained through team-work.
Intelligent textiles provide ample evidence of the potential and enormous wealth of
opportunities still to be realised in the textile industry in the fashion and clothing sector,
as well as in the technical textiles sector. Moreover, these developments will be the
result of active collaboration between people from a whole variety of backgrounds and
disciplines: engineering, science, design, process development, and business and
marketing. Our very day-to-day lives will, within the next few years, be significantly
regulated by intelligent devices and many of these devices will be in textiles and
clothing.
II. Definition and Classification of Smart Textiles:
Smart textiles are defined as textiles that can sense and react to environmental
conditions or stimuli from mechanical, thermal, chemical, electrical or magnetic
sources.
According to functional activity smart textiles can be classified in three categories [2]:
Passive Smart Textiles: The first generations of smart textiles, which can only sense the
environmental conditions or stimulus, are called Passive Smart Textiles.
Active Smart Textiles: The second generation has 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, vapour 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.
New fibre and textile materials, and miniaturized electronic components make the
preparation of smart textiles possible, in order to create truly usable smart clothes.
These intelligent clothes are worn like ordinary clothing, providing help in various
situations according to the designed applications.
During the continuation of this document, the two major ways for the manufacture of
SFIT, smart materials and electronic, will be detailed and illustrated with concrete
examples of obtained products.
III. New/Smart Materials and fibres used in Smart Textiles.
‘Smart’ or ‘Functional’ materials usually form part of a ‘Smart System’ that has the
capability to sense its environment and the effects thereof and, if truly smart, to respond
to that external stimulus via an active control mechanism. Smart materials and systems
occupy a ‘technology space’ which also includes the areas of sensors and actuators.
A summary of the smart materials used in textiles will be made, with some brief
descriptions of their applications.
III.1 Phase changing Materials for thermoregulation
III.1.1. Principle and Materials
Every material absorbs heat during a heating process while its temperature is rising
constantly. The heat stored in the material is released into the environment through a
reverse cooling process. During the cooling process, the material temperature decreases
continuously. A normal textile material absorbs about one kilojoule per kilogram of heat
while its temperature rises by one degree Celsius.
Comparing the heat absorption during the melting process of a phase change material
(PCM) with those in a normal heating process, a much higher amount of heat is
absorbed if a PCM melts. A paraffin-PCM, for example, absorbs approximately 200
kilojoules per kilogram of heat if it undergoes a melting process. In order for a textile to
absorb the same amount of heat its temperature would need to be raised by 200 K. The
high amount of heat absorbed by the paraffin in the melting process is released into the
surrounding area in a cooling process starting at the PCM's crystallisation temperature.
After comparing the heat storage capacities of textiles and PCM, it is obvious that by
applying paraffin-PCM to textiles their heat storage capacities can be substantially
enhanced [3].
During the complete melting process, the temperature of the PCM as well as its
surrounding area remains constant. The undesired temperature increase concomitant
with the normal heating process does not occur. The same is true for the crystallisation
process. During the entire crystallisation process the temperature of the PCM does not
change either. The high heat transfer during the melting process as well as the
crystallisation process without temperature change makes PCM an area of interest for
the heat storage.
In their application in textiles, the paraffins are either in solid or liquid state. In order to
prevent the paraffin's dissolution while in the liquid state, it is enclosed into small
plastic spheres with diameters of only a few micrometers. These microscopic spheres
containing PCM are called PCM-microcapsules. The microencapsulated paraffin is
either permanently locked in acrylic fibres and in polyurethane foams or coated onto the
surface of a textile structure.
PCM in textiles
III.1.2. Applications in Smart Textiles
Active wear needs to provide a thermal balance between the heat generated by the body
while engaging in a sport and the heat released into the environment. Normal activewear garments do not always fulfil this requirement. The heat generated by the body
during strenuous activity is often not released into the environment in the necessary
amount, thus resulting in a thermal stress situation. On the other hand, during periods of
rest between activities less heat is generated by the human body. Considering the same
heat release, hypothermia is likely to occur [4].
There are some commercial garments that possess microcapsule of PCM for example
the registered mark OUTLAST ®, that help to prevent theses kinds of discomfort. In
fact, in the case of heat generation PCM absorbs the energy thanks to the fusion of PCM
and in the case of cold exposition release heat thanks to the solidification process. This
system allows the thermoregulations of the garment and of it user.
III. 2. Shape Memory Materials
III. 2.1 Principle
There are two types of Shape memory materials [5]. The first classes are materials
stable at two or more temperature states. In these different temperature states, they have
the potential to assume different shapes, when their transformation temperatures have
been reached. This technology has been pioneered by the UK Defence Clothing and
Textiles Agency.
The other types of shape memory materials are the electroactive polymers which can
change shape in response to electrical stimuli. In the last decade there have been
significant developments in electroactive polymers (EAPs) to produce substantial
change in size or shape and force generation for actuation mechanisms in a wide range
of applications. In contrast to many conventional actuation systems, many types of
EAPs are also capable of providing sensing functions. EAPs can provide a range of
basic actuator mechanisms, force and displacement levels.
III.2.2 Materials
Shape memory alloys, such as nickel-titanium, have been developed to provide
increased protection against sources of heat. A shape memory alloy possesses different
properties below and above the temperature at which it is activated. Below this
temperature, the alloy is easily deformed. At the activation temperature, the alloy exerts
a force to return to a previously adopted shape and becomes much stiffer. The
temperature of activation can be chosen by altering the ratio of nickel to titanium in the
alloy [6].
Cuprous-zinc alloys are capable of a two-way activation and therefore can produce the
reversible variation needed for protection from changeable weather conditions. They
will also react to temperature changes brought about by variations in physical activity
levels.
Shape Memory Polymers have the same effect as the Ni Ti alloys but, being polymers,
they will potentially be more compatible with textiles. The first SMPs were
polynorborene-based with a Tg range of 35ºC to 40ºC developed by French CdF Chimie
Company. Later, several classes of SMPs based on mix of styrene – butadiene polyethylene Terephtalate - Polyetylene Oxyde – Polyurethane – Polycaprolactone –
etc… were developed with tg from -46°C to 125°C for a widening of the types of
application [5].
Electro active polymers EAPs are generally made up of high functionalised polymer.
One of the most famous EAPs is the “gel robots” made up of poly 2 –acrylamido -2methylpropane sulfonic acid that is fully researched for applications in the replacement
of muscles and tendons [7].
III.2.3 Applications in Smart Textiles
For clothing applications, the desirable temperatures for the shape memory effect to be
triggered will be near body temperature.
In practice, a shape memory alloy is usually in the shape of a spring. The spring is flat
below the activation temperature but becomes extended above it. By incorporating these
alloys between the layers of a garment, the gap between the layers can be substantially
increased above the activation temperature. Consequently, considerably improved
protection against external heat is provided [8].
Polyurethane films have been made which can be incorporated between adjacent layers
of clothing. When the temperature of the outer layer of clothing has fallen sufficiently,
the polyurethane film responds so that the air gap between the layers of clothing
becomes broader. This broadening is achieved if, on cooling, the film develops an outof-plane deformation, which must be strong enough to resist the weight of the clothing
and the forces induced by the movements of the wearer. The deformation must be
capable of reversal if the outer layer of clothing subsequently becomes warmer [9].
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.
The shape memory alloys can also contribute to the miniaturization of equipment and
systems, decrease the number of parts required and extend the life expectancy too due to
the favourable fatigue properties of the alloy.
Considerable progress still needs to be made with EAP technologies before
commercially viable applications. A multidisciplinary approach is essential for future
developments. Applications such as fabrics and textile structures will require fibre-like
EAP actuators and sensors in order to achieve effective integration. The large stimulated
displacements that have been observed have encouraged new thinking in terms of both
applications and designs. The natural ease of preparing and shaping such materials,
coupled with their low mass and large displacements, opens up new approaches in many
traditional areas as well as the potential to enable new technologies.
III.3 Chromic Materials
III.3.1 Definition
Other types of intelligent textiles are those which change their colour reversibly
according to external environmental conditions, for this reason they are also called
chameleon fibres [10]. Chromic materials are the general term referring to materials
which radiate the colour, erase the colour or just change it because its induction caused
by the external stimulus, as "chromic" is a suffix that means colour. Therefore we can
classify chromic materials depending on the stimulus affecting them [11] (in bold are
indicated those used in textile)
Photochromic: external stimulus is light.
Thermochromic: external stimulus is heat.
Electrochromic: external stimulus is electricity.
Piezorochromic: external stimulus is pressure.
Solvatechromic: external stimulus is liquid or gas.
III. 3.2. Materials and applications in Smart Textiles
Photocromic materials are generally reversible unstable organic molecules that change
of molecular configuration with the influence of a special radiation. The molecular
arrangement also perturbs the absorption spectra of the molecule and in consequences it
colour . The applications in textile are intended to the fashion area and only a few for
the solar protection. A T- Shirt made of photochromic prompted fabric was introduced
to the market in 1989 [12].
Thermochromic materials are those whose colour changes as a result of reaction to heat,
especially through the application of thermochromic dyes whose colours change at
particular temperatures. Two types of thermochromic systems that have been used
successfully in textiles are: the liquid crystal type and the molecular rearrangement type.
In both cases, the dyes are entrapped in microcapsules and applied to garment fabric
like a pigment in a resin binder [12].
The most important types of liquid crystal for thermochromic systems are the so-called
cholesteric types, where adjacent molecules are arranged so that they form helices.
Thermochromism results from the selective reflection of light by the liquid crystal. The
wavelength of the light reflected is governed by the refractive index of the liquid crystal
and by the pitch of the helical arrangement of its molecules. Since the length of the
pitch varies with temperature, the wavelength of the reflected light is also altered, and
colour changes result. An alternative means of inducing thermochromism is by means
of a rearrangement of the molecular structure of a dye, as a result of a change in
temperature [13].
The most common types of dye which exhibit thermochromism through molecular
rearrangement are the spirolactones, although other types have also been identified. A
colourless dye precursor and a colour developer are both dissolved in an organic
solvent. The solution is then microencapsulated and is solid at lower temperatures.
Upon heating, the system becomes coloured or loses colour at the melting point of the
mixture. The reverse change occurs at this temperature if the mixture is then cooled.
However, although thermochromism through molecular rearrangement in dyes has
aroused a degree of commercial interest, the overall mechanism underlying the changes
in colour is far from clear-cut and is still very much open to speculation [12].
Toray Industries reported in 1987 the development of a temperature sensitive fabric 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 colourneutralizer (alcohol etc.) which reacted and exhibited colour / decolour according to the
environmental temperature. SWAY was multicolour 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 temperature 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 [14].
Other types of SFIT
that use this effect are
the electrically warming
textiles (with Joules
effect) which change
colour with both the
effect of warm and
thermochromic
materials [15].
Uses of thermochromic inks by the International Fashion Machine [16]
In addition to the changing of colour due to reaction to light or heat there are other
chromic fibres presenting others characteristics. These fibres have raised the interest of
people because of their surprising and interesting nature. Therefore, there is the problem
that this "boom" will soon come to an end because these fibres are only considered to be
a temporary fashion material. In order to establish these fibres in everyday life it is
especially necessary to improve their endurance to light and to their accuracy.
Some of these fibres are those that present the phenomenon called solvate chromism
[17], whose colour changes when in contact with a liquid, for example water. These
materials are normally used for "design" swimsuits. Apart from this, the most important
application for chromic materials is fashion, to create fantasy designs changing its
colour depending on the volume of incident light.
III. 4. Luminescent Materials
III. 4.1. Definition
The difference between chromic and luminescent materials is that the first one changes
colour when the second one emits light thanks to a stimulus [18]. There are several
types of luminescent effects (in bold are indicated those used in textile):
- Photoluminescence: external stimulus is light. There are two types of
photoluminescent materials the fluorescent and the phosphorescent. The only
difference between the two is the time of emission.
- Opticoluminescence: conduction of light.
- Electroluminescence: external stimulus is electricity.
- Chemioluminescence: external stimulus is a chemical reaction.
- Triboluminescence: external stimulus is friction.
III.4.2. Materials and applications in Smart textiles.
There are two types of photoluminescent materials, the organic and the mineral. The
organics photoluminescent are rigid compounds (molecular or polymeric) which
possess a good molecular conjugation and that possess a relaxation mode that allow the
emission of a photon [19]. There are also mineral photoluminescent materials such as
some rare earth (europium, iridium). Photoluminecent materials are generally used in
textiles for application in dress for a night club and more interestingly in the marking of
labels with UV revelation materials for the detection of imitation goods and the security
label. Phosphorescent materials have been applied in inks which can store light and are
used in working clothes for road works/repairs in bad-light situations, or for marking
arrows on carpets to guide people during a power failure. The obtained effect is
generally known as glow in the dark [20].
Opticoluminescence is the typical effect encountered in optical fibres. The use of these
kind of technical fibres is now implanted for manufacturing textiles that emit light.
There are also applications with optical fibres at the development stage for the creation
of screens [21-22].
Opticoluminiscent curtains by LEITAT
As for photoluminescent materials, electroluminescent materials could be also organic
(molecular or polymeric) compounds or mineral materials [23]. Electroluminescent
compounds are, for this time, little used in textiles. The most common application result
form the use of electroluminescent yarn (constituted by mineral compounds) in the area
of fashion garments and also for high visibility protection equipments. However the
electroluminescent phenomena is now one of the most studied in the area of smart
textiles thanks to the emergence of the organic light emitting diodes [24] that possess a
flexible character and that are envisaged for the manufacture of flexible screens
adequate for the wearable computer.
Electroluminescent curtains made by the Interactive Institute of Design of Goteborg
[25].
III.5 Conductive materials
III. 5.1. Materials
There are two strategies to create electrical or thermal conductive fabrics and two types
of materials, the metals and the polymers. The same materials could be used for the both
conductivity (thermal and electric), because the two processes are similar and results of
an electronic agitation/conduction .
The first strategy uses high wicking finishes (ink) with a high metallic content that still
retains the comfort required for clothing. With the addition of nickel, copper, silver or
carbon coatings of varying thickness, these finishes provide a versatile combination of
physical and electrical properties for a variety of demanding applications [26].
The second strategy consists in the direct use of conductive yarns. The yarn could
constitute metal such as silver, copper, etc… or conductive polymer such as
polythiophene, polyaniline, and their derivatives [27].
Although there are many different trade marks commercialising these materials, they all
have the same main properties. They are lightweight, durable, flexible and cost
competitive and they are able to be crimped and soldered and subjected to textile
processing without any problems.
Examples of conductive yarns and inks used in textiles
III. 5.2. Applications in Smart Textiles
Two of the main applications for conductive materials are electromagnetic interface
(EMI) shielding and conducting thanks to their particular properties, which are listed
below. Conductive fibres braided into a shield or sock offer superior performance
against electromagnetic interference [28], antistatic [29], and they present the following
advantages:
These materials also increase thermal conductivity using metal over conventional
polymers and are used in clothing offers sports apparel with the minimum of thermal
insulation. Another type of fibres included in this group is carbon fibres.
The structure of these materials offers the capability of reading the location, within a
fabric sheet, of a pressure point (such as a finger press). It is possible to incorporate this
function into an elastic sheet structure, allowing the sheet to conform to many 3-D
shapes, including compound curves, while still accurately measuring an X-Y position.
Readings can be obtained from smart fabrics according to force and area. This allows
the user to differentiate between separately identified inputs ranging from high-speed
impact to gentle stroking. The force/area reading is versatile, as fabrics can be
constructed to be more sensitive to either force or area. Through this new technology, a
pressure sensitive capability can be incorporated almost invisibly into textiles without
significantly increasing their cost or compromising any of their properties [30].
There are other applications for conductive materials such as heated clothes for extreme
winter conditions or heated diving suits to resist very cold water. In these cases an
electrical energy source is needed in order that the material generates energy due to the
Joules effect. The thermal conduction that allows distribution of heat throughout the
entire garment or suit [31].
There are also some applications for conductive garments in the domain of the antenna
due to their capacities to receive electromagnetic waves [32].
Finally, some of the main applications of conductive textile materials are their uses for
the power supply of electronic devices in the garments, the second main area of the
SFIT.
III. 6 Membranes
III.6.1 Materials
Multi-disciplinary research led to the successful development of the cutting-edge
technology of laminating a variety of microporous or hydrophilic membranes. The
membranes are constituted of polymers and their structure could be made of one or
more layers (until 6 layers) according to the wanted properties. Membranes are
deposited on textiles in order to add new properties onto theirs surfaces. The polymers
used in the membranes may be of several natures such as biopolymer (generally
cellulosic), or synthetic as the ployfluorocarbone or the polyurethanes and theirs
derivatives [33].
The indestructible membrane Texflex by INVENT Umwelt [34].
III.6.2 Applications in Smart Textiles
One of the main applications of membranes is in the field of sportswear for the
manufacture of breathable and impermeable clothes. Indeed, with a simple system of
membrane, fabrics possessing an excellent water exchange are obtained with a good
elimination of the sweat at the garment interface (breathability) and the creation of an
external barrier with extreme water repellence.
For example, the best provider of textile membranes is Gore that manufactures unique
wafer-thin microporous membrane (Gore tex), which contains over 9 millions pores per
square inch. Each pore is 20,000 times smaller than a water droplet, yet some 700 times
bigger than a moisture vapour molecule. This gives the fabric the excellent levels of
waterproofness and breathability that the brand is famous for. Gore-Tex is a bicomponent membrane, meaning that it is made up of two parts. The main part (that you
see) is made from expanded polytetrafluoroethylene (ePTFE for short). This is then
combined with an oleophobic (oil hating) layer that protects the membrane from the
natural oils that the human body emits, insect repellents, cosmetics etc. The outer face
of the Gore-Tex fabric is coated with a hydrophobic DWR (Durable Water Repellency)
treatment which encourages surface water to bead up and run off, improving the wet
weather performance of the garment and promoting breathability by preventing wettingout of the outer face.
Another successful application of the membranes in intelligent textiles is the Lotus
effect [35]. Lotus effect results in an ultrahydrophobic finishing (membranes or coating)
which provides repellence of the aqueous products and also of the oleic product. The
result is that the garment does not have an affinity with any products so that it can not
be dirtied. Another name of this property is self-cleaning garments. Several commercial
products exist which use membrane of polytetrafluoroethylene derivatives that present
an analogy with the Lotus effect [36].
III.7 Photovoltaic materials
III.7.1 Principle and materials
The photovoltaic effect has been discovered in 1839 by Becquerel. Photovoltaic
materials possess the property to generate electric current by means of a light excitation.
The mechanisms of electricity generation could be effectuated by two processes:
- The first way is the separation of charges at a p-n junction in a device. The
materials used are semiconductor and are generally based on doped silicon.
At the p-n junction electrons and holes are separated and form an electric
current in the bulk of semiconductor. The extraction from the devices of both
species by means of appropriated electrodes allows the generation of the
electricity.
- The second way is obtain thanks to the inverse process of
electroluminescence. The materials used are also semiconductor but more
organic or sensitive to light (molecules, polymers, dendrimers). The
reception of an appropriate light allows to compounds to pass in an excited
state. At the excited state the electron is in the LUMO and the hole in the
HOMO. If the electrodes and the power of separation of charges are adapted,
the electron and the hole are separated and allow the formation of the
current.
Actually, silicon solar cell are widely commercialised and depending the crystalline
state of the silicon the energy conversion efficiency could vary between 6% for
amorphous to 30% for crystalline. It also exist thin film solar cells that are essentially
composed of Cadmium telluride, copper indium selenide (CIS) or copper indium
gallium selenide (CIGS), the efficiency of this solar cells are between 11-14%, and they
are very interesting for their weight and thin film characters for application in textile.
Finally, the organic solar cells are also very promising for textile applications but they
possess low efficiency, on average 5%. For this time the organic solar cells are in
development, and numerous chemists work on their molecular compositions, the
expectancies for this technology are very high in the future five years.
III.7.2 Application in textile
The main application of solar cells in textile is the electric alimentation of integrated
electronic devices, e-textile. The alimentation could be made directly from the solar cell
to the devices but the majority of encountered solutions are using of solar for charging
batteries that could deliver energy to the appropriate device. Recharging mobile phone,
Mp3 player.
.
Examples of uses of solar cells on textile substrate.
Nowadays, a new field of investigation consists in the deposition of photovoltaic
devices on textile substrates. Recently, a multidisciplinary team of German searchers
have presented results of a textile supported CIGS solar cell that obtain efficiency of
8.3%.
Majority of smart materials are used in textile industry for their intrinsic properties.
Another way to profit from smart materials in the textile area is by using theirs
capacities as sensors in electronic devices.
IV. Electronic textiles
As introduced at the beginning of this document, the other field of investigation and
development in SFIT is the integration of miniaturised electronics as sensors and
microchips, in order to detect and analyse stimuli and provide the adequate response.
These kinds of development have several names as e-textile, textronics, etc…[2]
Several efforts have been made in this field during the last 10 years essentially for
garments used by soldiers or in the medical area [37]. When incorporated into the
design of clothing, the technology could quietly monitor the wearer's heart rate, EKG,
respiration, temperature, and a host of vital functions, alerting the wearer or physician if
there is a problem.
It is really difficult to relate all the works made in this R&D topic, so only the most
famous and the most useful will be described.
IV.1. Textiles that sensor the body for military or medical uses
IV.1.1. The Smart shirt by the Professor Sundaresan Jayaraman
Georgia Tech was the pioneering institute for the development of SFIT that integrates
electronics. During a project funded by the US Naval Department in 1996, they have
developed a "Wearable Motherboard" (GTWM commercial name is Smart shirt) [3839], which was manufactured for use in combat conditions. The garment uses optical
fibres to detect bullet wounds and special sensors that interconnect in order to monitor
vital signs during combat conditions. Medical sensing devices that are attached to the
body plug into the computerised shirt, creating a flexible motherboard. The GTWM is
woven so that plastic optical fibres and other special threads are integrated into the
structure of the fabric. The GTWM identifies the exact location of the physical problem
or injury and transmits the information in seconds. This helps to determine who needs
immediate attention within the first hour of combat, which is often the most critical
during battle.
Furthermore, the types of sensors used can be varied depending on the wearer's needs.
Therefore, it can be customised for each user. For example, a fire-fighter could have a
sensor that monitors oxygen or hazardous gas levels. Other sensors monitor respiration
rate and body temperature, etc.
Left: The GTMW of the Georgia Tech, Right: The Smart Shirt by Sensatex [40]
The smart shirt could be used in a large variety of fields and the Sensatex company
currently manufacture it for commercial applications such as:
Medical Monitoring
Disease Monitoring
Infant Monitoring
Athletics
Military Uses
IV.1.2 The electronic bra
Professor Malcolm McCormick of the De Montfort University have developed a new
device using tiny electrical currents, which are passed through the breast, working on
the principle that the differences between healthy breast tissue and tumour tissue affect
the way the current gets through [41]. According to the researchers, the denser tissue in
tumours makes it harder for the electricity to get through, and sensitive measuring
equipment picks this up. The researchers stated that by scanning the breast from
different angles, a detailed map on which abnormal growth stands out could be
constructed on a computer. The technology could become available here within one
year and may allow a self and rapid diagnostic of the presence of tumour in the breast.
IV.1.3 The sensory Baby Vest
At the ITV Denkendorf, an interdisciplinary team of researchers has been developing a
special vest for babies [42]. The sensory baby vest is equipped with sensors that enable
the constant monitoring of vital functions such as heart, lungs, skin and body
temperature which can be used in the early detection and monitoring of heart and
circulatory illness. It is hoped to use this vest to prevent cot death and other lifethreatening situations in babies. The sensors are attached in a way that they do not pinch
or disturb the baby when it is sleeping.
ITV’s Sensory Baby Vest [43]
IV.1.4 The life shirt by Vivometrics
The LifeShirt System is the first non-invasive, continuous ambulatory monitoring
system that can collect data on pulmonary, cardiac and other physiologic data, and
correlate them over time. The LifeShirt System gathers data during the subject's daily
routine, providing pharmaceutical and academic researchers with a continuous "movie"
of the subject's health in real-life situations (work, school, exercise, sleep), rather than
the "snapshot" generated during a typical clinic visit. The LifeShirt System collects,
analyses and reports on the subject's pulmonary cardiac and posture data. It also
correlates data collected by optional peripheral devices that measure blood pressure,
blood oxygen saturation, EEG, EOG, periodic leg movement, core body temperature,
skin temperature, end tidal CO2, and cough [44-45].
The LifeShirt System features an enhanced, ambulatory version of respiratory inductive
plethysmography (RIP), the gold standard for respiratory monitoring. RIP is used in
more than 1,000 hospital intensive care units worldwide. It is ideal for monitoring the
accurate tidal volume of all subjects, including those who are unable to use spirometers
due to age or other factors. The LifeShirt System is available in adult and pediatric (ages
5-17) sizes and is used in clinical trials and research. It is available as a prescription
medical device and is not sold directly to consumers.
IV.2. Interactive Fabrics
In our society communication tools, interactivity and portable devices are one of the
largest sources of innovation and represent a tremendous market. The integration of
portable electronics devices in textiles appeared as a natural market.
The first innovation was a keyboard made in a single layer of fabric using capacitive
sensing, where an array of embroidered or silk-screened electrodes make up the points
of contact [46]. A finger's contact with an electrode can be sensed by measuring the
increase in the electrode's total capacitance. It is worth noting that this can be done with
a single bidirectional digital I/O pin per electrode, and a leakage resistor sewn in highly
resistive yarn. Capacitive sensing arrays can also be used to tell how well a piece of
clothing fits the wearer, because the signal varies with pressure.
The keypad shown here has been mass-produced using ordinary embroidery techniques
and mildly conductive thread. The result is a keypad that is flexible, durable, and
responsive to touch. A printed circuit board supports the components necessary to do
capacitive sensing and output keypress events such as a serial data stream. The circuit
board makes contact with the electrodes at the circular pads only at the bottom of the
electrode pattern. In a test application, 50 denim jackets were embroidered in this
pattern. Some of these jackets are equipped with miniature MIDI synthesizers
controlled by the keypad. The responsiveness of the keyboard to touch and timing were
found by several users to be excellent.
Several versions of capacitive or flexible keyboards in textile materials [46-47]
There are several commercial products that are inspired by this keyboard. The most
famous are the KENPO jacket that possesses an integrated MP3 lectors and the Ipods
jeans by Levis[48].
There are also many efforts effectuated for the integration of mobile phones in
garments. A Swedish R&D team has developed a glove that incorporates a phone.
A glove that integrates a mobile phone [49]
IV.3 Comfort
One of the best examples for improving comfort thanks to electronics is an Australian
invention: the Smart Bra. Wallace et. al at the University of Wollongong, have
developed a bra that will change its properties in response to breast movement. This bra
will provide better support to active women when they are in action [50]. The 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 the 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 stiffening cups when it detects excessive
movement.
The Smart Bra [50]
IV.4 Security
The first security tools developed thanks to the electronic textile possibility is the Radio
Frequency Identification tags. RFID tags are miniscule microchips, which have already
shrunk to half the size of a grain of sand. They listen for a radio query and respond by
transmitting their unique ID code. Most RFID tags have no batteries: They use the
power from the initial radio signal to transmit their response.
The primary use of RFID in textile rental has, to date, centred on automating the
garment handling process, including: check-in, sorting, and checkout. RFID systems in
textile rental can eliminate significant manual labour. However, the RFID systems
generate significant improvements in customer satisfaction fewer distribution errors,
traceability. For theses reasons, a lot of prestigious brand names will shortly adopted the
RFID tags system in order to fight adequately the falsification of their products [51].
Other types of innovations in the area of security are the integration of GPS in garments
for the detection of user position in case of disappearance or kidnapping. The company
Interactive Wear AG has presented a pilot prototype in March 2006 of these
technologies that will have a lot of applications in extremes sports clothes, children
garments, etc [52].
IV. 5. The wearable computer
There are several investigation groups that work on one of the most amazing e-textiles
solutions, the wearable computer [53]. The main objective is the integration of a
complete computer screen, CPU and keyboard in a wearable garment. Currently, there
are no commercial goods which respond to these incredible products. Indeed some
prototypes have been presented such as the Boeing Computer Services developed by
Honeywell Ind. Virtual Vision, Carnegic Melloon University and some other research
organisations are developing a wearable computer system that is a better powered
computer system worn on the user's body (on a belt, backpack or vest).
The wearable computer [54].
V. Conclusions
A few years ago, smart textiles were presented as imaginary products and as a non
competitive market. After scientific efforts and development phases, nowadays SFIT are
an implanted customer interest and are presented as the future of the textile industry. A
lot of commercial products are available and, as it was presented during this document,
a lot of scientist are developing new solutions, ideas and concrete products. Some
approximations announce a market of 1 billion dollars by 2010 which certainly explains
the current passion for these news topics.
Acknowledgement.
This work have been supported by the MATEO project a Regional Framework
Operation (RFO) in the framework of the Interreg IIIC.
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