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A Historical Review of the Development of Electronic Textiles

Authors:

Abstract

Textiles have been at the heart of human technological progress for thousands of years, with textile developments closely tied to key inventions that have shaped societies. The relatively recent invention of electronic textiles is set to push boundaries again and has already opened up the potential for garments relevant to defense, sports, medicine, and health monitoring. The aim of this review is to provide an overview of the key innovative pathways in the development of electronic textiles to date using sources available in the public domain regarding electronic textiles (E-textiles); this includes academic literature, commercialized products, and published patents. The literature shows that electronics can be integrated into textiles, where integration is achieved by either attaching the electronics onto the surface of a textile, electronics are added at the textile manufacturing stage, or electronics are incorporated at the yarn stage. Methods of integration can have an influence on the textiles properties such as the drapability of the textile.
fibers
Review
A Historical Review of the Development of
Electronic Textiles
Theodore Hughes-Riley * ID , Tilak Dias and Colin Cork
Nottingham Trent University, Advanced Textiles Research Group, School of Art & Design, Bonington Building,
Dryden St, Nottingham NG1 4GG, UK; tilak.dias@ntu.ac.uk (T.D.); colinrcork@googlemail.com (C.C.)
*Correspondence: theodore.hughesriley@ntu.ac.uk; Tel.: +44-(0)-11-5941-8418
Received: 13 February 2018; Accepted: 23 May 2018; Published: 31 May 2018


Abstract:
Textiles have been at the heart of human technological progress for thousands of years,
with textile developments closely tied to key inventions that have shaped societies. The relatively
recent invention of electronic textiles is set to push boundaries again and has already opened up the
potential for garments relevant to defense, sports, medicine, and health monitoring. The aim of this
review is to provide an overview of the key innovative pathways in the development of electronic
textiles to date using sources available in the public domain regarding electronic textiles (E-textiles);
this includes academic literature, commercialized products, and published patents. The literature
shows that electronics can be integrated into textiles, where integration is achieved by either attaching
the electronics onto the surface of a textile, electronics are added at the textile manufacturing stage,
or electronics are incorporated at the yarn stage. Methods of integration can have an influence on the
textiles properties such as the drapability of the textile.
Keywords: electronic textiles; E-textiles; smart textiles; intelligent textiles
1. Introduction
This historical review will provide the reader with an insight into the development and
employment of electronic textiles. While some academic sources have been used, a strong focus
has been placed upon patented technology and commercialized products, which are often neglected in
reviews of the literature.
The innovation of textiles 27,000 years ago could be contested as humanity’s invention of the
first material [
1
]. The passing of the millennia has consolidated humanity’s need of textiles either
to be protected from the environment, or desire to outwardly convey a message about themselves;
whether that be artistic, stylistic, or wealth-related. The creation of textiles has therefore been coupled
closely with key inventions that have shaped society; the knitting frame by William Lee in 1589 [
2
],
the flying shuttle by John Kay in 1733 and the spinning jenny by James Hargreaves around 1765 [
3
],
and set the foundation for the first industrial revolution.
A new revolution is now underway where the most widely used material by humankind has
gained new functionality with the incorporation of electronic components. The first examples of
electronic textiles date back to the use of illuminated headbands in the ballet La Farandole in 1883 [
4
].
More recently advances have appeared due to the reducing size and cost of electronic components,
as well as an increased complexity of small-scale electronics, and have begun to show the true scope of
possibilities for integrating electronics with clothing.
The growth of E-textiles in the later part of the 20th Century was due to a series of developments
in material science and electronics further expanding the potential scope for embedding electronics
within clothing. The conductive polymer was a key innovation; invented by Heeger et al. in 1977 [
5
]
this led to a Nobel Prize thirty-three years later [
6
]. A patent for this type of technology for use with
Fibers 2018,6, 34; doi:10.3390/fib6020034 www.mdpi.com/journal/fibers
Fibers 2018,6, 34 2 of 15
textiles was granted shortly after its creation [
7
]. Another critical development were advancements
in transistor technology, with the creation of the first MOS (metal–oxide–semiconductor field-effect
transistor) in 1960 [
8
]. The use of transistor-based electronics were outlined in a patent describing
illuminated clothing from 1979 [9].
For a greater adoption of E-textiles a better level of integration of the electronic components
was required. Key patents from 2005, 2016 and 2017 described the encapsulation of semi-conductor
devices within the fibers of yarns [
10
12
]. This represented the start of the work on electronically
functional yarns.
Three different pathways have been used to integrate electronics into textiles. These three distinct
generations of electronic textiles are adding electronics or circuitry to a garment (first generation),
functional fabrics such as sensors and switches (second generation), and functional yarns (third generation).
Prior to the creation of E-textiles there are also many examples of the use of conductive fibers in textile
fabrication, going back as far as the second century [
13
]. A timeline showing the evolution of E-textiles is
given by Figure 1.
Fibers 2018, 6, x FOR PEER REVIEW 2 of 15
this led to a Nobel Prize thirty-three years later [6]. A patent for this type of technology for use with
textiles was granted shortly after its creation [7]. Another critical development were advancements
in transistor technology, with the creation of the first MOS (metal–oxide–semiconductor field-effect
transistor) in 1960 [8]. The use of transistor-based electronics were outlined in a patent describing
illuminated clothing from 1979 [9].
For a greater adoption of E-textiles a better level of integration of the electronic components was
required. Key patents from 2005, 2016 and 2017 described the encapsulation of semi-conductor
devices within the fibers of yarns [10–12]. This represented the start of the work on electronically
functional yarns.
Three different pathways have been used to integrate electronics into textiles. These three
distinct generations of electronic textiles are adding electronics or circuitry to a garment (first
generation), functional fabrics such as sensors and switches (second generation), and functional yarns
(third generation). Prior to the creation of E-textiles there are also many examples of the use of
conductive fibers in textile fabrication, going back as far as the second century [13]. A timeline
showing the evolution of E-textiles is given by Figure 1.
Figure 1. A timeline of the different generations of electronic textiles. This timeline shows when
significant interest in the technology began, and not earlier, isolated instances.
Each method of integration will have an influence on the textile properties such as the shear
properties of the textile, or its flexibility, both of which effect the drapability. Figure 2 shows examples
of each generation of electronic textiles.
Figure 2. Photographs showing contemporary examples of each generation of electronic textile. (Left)
An Adafruit coin cell battery holder. The first generation saw devices affixed to textiles. (Middle) A
knitted electrode. The second generation of electronic textiles describes functional fabrics where
conductive elements are integrated into a textile. (Right) An example of functional yarns (in this case
LED yarns). The third generation of electronic textiles describe electronics embedded into textiles at
a yarn level.
For the purposes of this review it is important to disentangle the various terms used loosely in
the field of advanced textiles. Electronic textiles will be discussed; the strict definition of electronic
textiles are where electronically conductive fibers or components are incorporated into a textile
(electronic textiles will be referred to as ‘E-textiles’ in the subsequent text). Here, the term smart
Figure 1.
A timeline of the different generations of electronic textiles. This timeline shows when
significant interest in the technology began, and not earlier, isolated instances.
Each method of integration will have an influence on the textile properties such as the shear
properties of the textile, or its flexibility, both of which effect the drapability. Figure 2shows examples
of each generation of electronic textiles.
Fibers 2018, 6, x FOR PEER REVIEW 2 of 15
this led to a Nobel Prize thirty-three years later [6]. A patent for this type of technology for use with
textiles was granted shortly after its creation [7]. Another critical development were advancements
in transistor technology, with the creation of the first MOS (metal–oxide–semiconductor field-effect
transistor) in 1960 [8]. The use of transistor-based electronics were outlined in a patent describing
illuminated clothing from 1979 [9].
For a greater adoption of E-textiles a better level of integration of the electronic components was
required. Key patents from 2005, 2016 and 2017 described the encapsulation of semi-conductor
devices within the fibers of yarns [10–12]. This represented the start of the work on electronically
functional yarns.
Three different pathways have been used to integrate electronics into textiles. These three
distinct generations of electronic textiles are adding electronics or circuitry to a garment (first
generation), functional fabrics such as sensors and switches (second generation), and functional yarns
(third generation). Prior to the creation of E-textiles there are also many examples of the use of
conductive fibers in textile fabrication, going back as far as the second century [13]. A timeline
showing the evolution of E-textiles is given by Figure 1.
Figure 1. A timeline of the different generations of electronic textiles. This timeline shows when
significant interest in the technology began, and not earlier, isolated instances.
Each method of integration will have an influence on the textile properties such as the shear
properties of the textile, or its flexibility, both of which effect the drapability. Figure 2 shows examples
of each generation of electronic textiles.
Figure 2. Photographs showing contemporary examples of each generation of electronic textile. (Left)
An Adafruit coin cell battery holder. The first generation saw devices affixed to textiles. (Middle) A
knitted electrode. The second generation of electronic textiles describes functional fabrics where
conductive elements are integrated into a textile. (Right) An example of functional yarns (in this case
LED yarns). The third generation of electronic textiles describe electronics embedded into textiles at
a yarn level.
For the purposes of this review it is important to disentangle the various terms used loosely in
the field of advanced textiles. Electronic textiles will be discussed; the strict definition of electronic
textiles are where electronically conductive fibers or components are incorporated into a textile
(electronic textiles will be referred to as ‘E-textiles’ in the subsequent text). Here, the term smart
Figure 2.
Photographs showing contemporary examples of each generation of electronic textile.
(
Left
) An Adafruit coin cell battery holder. The first generation saw devices affixed to textiles.
(
Middle
) A knitted electrode. The second generation of electronic textiles describes functional fabrics
where conductive elements are integrated into a textile. (
Right
) An example of functional yarns (in this
case LED yarns). The third generation of electronic textiles describe electronics embedded into textiles
at a yarn level.
For the purposes of this review it is important to disentangle the various terms used loosely in the
field of advanced textiles. Electronic textiles will be discussed; the strict definition of electronic textiles
Fibers 2018,6, 34 3 of 15
are where electronically conductive fibers or components are incorporated into a textile (electronic
textiles will be referred to as ‘E-textiles’ in the subsequent text). Here, the term smart textiles, often
anachronistically used as a synonym for electronic or E-textiles, will not be employed unless the textile
has some kind of intelligence.
Critically, this historical review of the literature has a strong focus on innovation including
patented technology and commercialized products, making heavy use of patents and internet sources.
Non-internet sources have been referenced wherever possible; however, in many cases, particularly
for products, only websites exist. These are areas that are typically neglected and this review serves as
a complimentary piece to other more traditional reviews with the academic literature as the focus.
As a historic review this work will principally focus on research prior to 2010. Interest in electronic
textiles has increased significantly since 2010. A search of the literature using the term ‘electronic
textiles’ yields 310,000 results of which 254,000 are between 2010 and 2018. For completeness some
more contemporary resources will be examined, for example in the area of textile energy solutions,
which has largely evolved since 2010. There are several excellent reviews covering more recent
developments in electronic textiles [1416] and recent books on this subject [17,18].
The aim of this review is to overview the key pathways to the development of electronic textiles.
The review is structured over ten sections, with the seven sections covering examples from a specific
types of E-textile or application, such as sensors or illumination. Each section covers a major area of
research in the literature, for example, temperature control textiles. In some cases two areas of interest
have been grouped together such as E-textile pressure sensors and textile switches as one of these
technologies led to the other. Three final sections discuss market trends, possible future developments
for E-textiles, and a brief conclusion.
2. Temperature Control Textiles
It is unsurprising that the use of embedded conductive fibers was employed in one of the first
true E-textiles, the electrically heated glove patented in 1910 [
19
]. This invention used ohmic heating
(Joule heating, or resistive heating [
20
]), where an electric current was run through the conductive
fibers and the electric resistance in the wires led to a heating effect. This type of heating was the
core application of many early E-textiles. Other patents refining the heated gloves were filed [
21
,
22
],
and variations on the theme appeared such as the heated boot [
23
], and full heated garments including
a jacket element [
24
,
25
]. The knitted heater was patented in 1910 [
26
]. Heated gloves and jackets based
on these core concepts are still available today showing the relevance of these early innovations.
Other devices utilizing heating elements were created between the 1930s and 1970s included the
heated blanket [
27
], a heated baby carriage blanket [
28
], and electrically heated socks [
29
]. The year
1968 is often seen as the birth of modern E-textiles, when the Museum of Contemporary Craft in
New York City held an exhibition, Body Covering, exploring a series of electric garments with
functions such as heating and cooling [30].
Interest in developing new heated textiles remained well into the 21st Century with a patent
from 2008 describing the incorporation of inductive heating elements into footwear and apparel [
31
].
Commercially, EXO Technologies have produced heated gloves that can be used by militaries or for
a variety of outdoor activities such as skiing or motorcycling [
32
]. Marktek also make conductive
textiles [
33
] that include heating products. WarmX produce heated clothing [
34
]. In addition to heating,
a paper in 2012 described a wearable textile-based cooling system using thermoelectric modules and
refrigerant channels [35].
3. Materials Developments and Wearable Computing
Wearable computing is a type of wearable that contains information technology, and is able to
store, manipulate, or transmit data. The inclusion of wearable computing is what makes an E-textile
a smart textile. The 1990s and early 2000s saw patents for devices either integrated onto the surface
of garments or contained within pockets beginning to emerge [
36
42
]. These are generally regarded
Fibers 2018,6, 34 4 of 15
as the first generation E-textiles, where an electrical circuit or electronic components were attached
to a garment. The initial commercialized ‘first generation E-textile’ garments began to appear on the
market with the Industrial Clothing Division plus-jacket in 2000 [
43
]. This jacket attached electronic
devices into pockets.
An important component towards the successful development of wearable computing included
methods of creating electronic circuits within textiles. Post et al. filed a patent in the late 1990s
describing how to integrate devices and circuits into textiles [
44
]. Another patent described using
electrically insulating and electrically conductive yarns woven into a garment to create an electronic
circuit [
45
]. A later patent further built on the use of knitting techniques to create electrical circuits
and pathways [
46
]. In 2006 Ghosh et al. described an in-depth means of forming electrical circuits
within textile structures [
47
]. Textilma were granted a patent describing an elastic compound thread
with electrical conductivity [
48
]. A patent two years later from Seoul National University described
a system for power transmission using conductive sewing thread [
49
]. An E-textile patents published
in 2006 discussed the inclusion of devices such as Bluetooth and the electrical connections required
between components [
50
]. With the concept of wearable computing existing for a number of years,
in 2006 Frost and Sullivan provided an excellent review of wearable computing at that time [51].
A variety of other developments linked to wearable computing appeared in the 2000s.
WearIT@work [
52
] was a project funded by the European Commission (
14.6 million) to investigate
wearable computing. A particular focus was user acceptance. The European Space Agency
(ESA) iGarment project was developed to create an Integrated System for Management of Civil
Protection Units. The project was targeted to make a full-body smart garment. This would have
incorporated sensors for monitoring vital signs and position. The garment was also to have included
a communications unit and GPS [53].
Some recent developments in wearable computing have veered away from textiles including the
Google Glass [
54
]. Despite these devices being wearables and not textiles, textile computing has still
made significant strides in recent years.
Graphene technology may be a key contributor to the further development of wearable computing.
The US Army Research Laboratory discussed the potential of graphene-based nano-electronics for
applications in wearable electronics in a report produced in 2012 [
55
]. Interfacing with E-textiles is
also of importance for future developments: A recent Microsoft patent described an interface system
for using muscle movements to control a computer or other device [56].
The use of organic conductive polymers may also improve the potential for wearable computing.
Hamedi et al. have developed a fiber-level electrochemical transistor, opening up the potential to
create larger circuits using a weave of these fibers [57].
4. Sensors
The development of E-textiles in an academic setting first gained traction in the late 1990s
with a series of publications from the Massachusetts Institute of Technology (MIT) and the Georgia
Institute of Technology [
58
]. The ‘The Wearable Motherboard
TM
’ proposed a smart-shirt capable of
un-obstructively monitoring human life signs [59].
Work by Farringdon et al. described a functional fabric in the form of a woven stretch sensors
later 1990s. They produced a fabric stretch sensors for the monitoring of body movement [60].
A master’s thesis from the US Naval Postgraduate School in 2006 identified a further potential
use of wearable sensors, suggesting that they may prove beneficial to locate sniper fire in combat
situations [61].
Health and wellbeing applications also gained interest in the 2000s, with Cooseman et al. [
62
]
describing a garment with an embedded patient monitoring system, which included wireless
communication and inductive powering. In this instance, the garment was designed for infants.
A paper in 2008 described a process for transforming cotton thread for use in E-textiles by applying
carbon nanotubes [
63
]. It was claimed that the technology could be used for bio-sensing with a key
Fibers 2018,6, 34 5 of 15
result of the paper being that the carbon nano-tube cotton threads could be used to detect albumin,
which is an important protein in the blood.
Work has investigated the use of textile electrodes for heart rate monitoring or ECG
(Electrocardiogram). MyHeart was an EU (FP 6) funded project to develop smart fabrics for both ECG
and respiration [
64
], with the project concluding in 2009. Another EU FP 6 project, CONTEXT,
also investigated the use of textile electrodes, in this case to measure muscle and heart electric
signals [65].
A paper from 2009 described an integrated temperature sensor [
66
]. Also in 2009, a report
described the development of a knitted biomedical sensor for the monitoring body temperature [
67
].
A patent was granted for a linear electronic transducer for strain measurement in 2011 [68].
A proliferation of sensor embedded garments began to emerge on the market with the company
Clothing+ producing both the Sensor Belt [
69
] and the Pure Lime sensor bra. Both devices focused on
the active-wear market. At the time of writing it is unclear whether the Pure Lime sensor bra is still
in production. Other active-ware devices have included the Adidas MiCoach heartrate monitoring bra.
Despite interest by a number of media outlets [
70
], at the time of writing it appears that this product is
no longer sold by Adidas.
The incorporation of sensors into garments has also continued to generate interest in the literature
and from companies. A 2011 paper from described the development of a socks with integrated
strain sensors for monitoring foot movement. Such systems could have had applications in stroke
rehabilitation [
71
]. There have also been other example of incorporating temperature-sensing elements
into textiles [7275].
A variety of textile-based sensors and sensing garments have also appeared on the market.
Nypro (formerly Clothing+) produces textile-based sensor systems [
76
]. Ohmatex [
77
] has created textile
conductors and sensors. Polar [
78
] sell wearable monitoring equipment, including heartrate monitors.
SmartLife [
79
] produce knitted physiological measurement devices for healthcare, sports and
military applications. The Zephyr BioHarness [
80
] takes physiological meassurements from the wearer.
The recorded data can then be transmitted. Under Armour have produced a shirt that monitors biometric
data [81].
5. E-Textile Pressure Sensors and Textile Switches
Many early functional fabrics took the form of textile switches [
82
] and this area of research
was expanded upon heavily by academia. The work of Post et al. included the development of
a textile-based keyboard using embroidered electrodes with a silk and twisted gold spacer fabric [
83
].
This technology was the first step forwards pressure sensitive fabrics.
Further developments into textile transducers came in a paper from 2004 which described knitted
transducers for motion and gesture capture together with ECG (electrocardiogram) measurement [
84
],
which was also patented [
85
]. A related paper from 2005 described knitted capacitive transducers for
touch and proximity sensing [86].
Sergio et al. initially proposed a textile based capacitive pressure sensor where a three-layer
structure was implemented with a layer of rows of conductive fibers, an elastic spacer foam, and then
another layer of conductive fibers orientated perpendicular to the top layer [
87
]. Their work described
four methods for producing the conductive tracks; weaving in a mix of conductive and insulating
fibers, embroidering the circuit using conductive thread, textile electrodes separated by conducting
strips (called bundle routing in the paper), and the use of conductive paint. A follow-up paper
described a measurement system in combination with their E-textile that was capable of producing
pressure images [
88
]. Other researchers also developed this type of technology. Mannsfeld et al.
developed a highly flexible and inexpensive capacitive pressure sensor using a micro-structured thin
film as the capacitors dielectric layer [
89
]. Takamatsu et al. fabricated a pressure sensitive textile
using a perfluoropolymer spacer, and rows of woven, die-coated yarns to make conductive rows [
90
].
Meyer et al. have contributed to the development of textile pressure sensors. Their general pressure
Fibers 2018,6, 34 6 of 15
sensor design consisted of three parts, an embroidered set of 2 cm
×
2 cm electrodes, a 3D-knitted
spacer fabric, and a woven back electrode [
91
,
92
]. Hoffmann et al. used a similar principle for a system
to measure respiratory rate, where two conductive fabrics were placed on either side of a 3D-spacer
textile [
93
]. A different proposal to monitor respiratory rate has used the change in induction of two
knitted coils as the coils moved [94].
Holleczek et al. created a sensor using a pair of textile electrodes and a proprietary resin spacer
material, integrating the sensor into socks [
95
]. Other capacitive textile designs have included
a capacitive fiber by Gu et al. [
96
]. The capacitive fiber consisted of a conducting copper wire
(0.12 mm diameter) embedded within a fiber. A similar design was employed by Lee et al. where
a conductive coating was applied to a Kevlar fiber, which was then coated in a Polydimethylsiloxane
(dielectric) layer. Capacitive junctions seen where the two fibers intersected [
97
]. Other copper wires
were wrapped around the fibers surface acting as the second electrode.
Pressure sensing textiles have not been limited to a research environment. Commercially, Novel
sell a number of pressure sensing products including insoles, seating covers, and gloves [
98
].
The XSENSOR
®
Technology Corporation have focused on seating sensors (in particular for the
automotive industry), health care monitoring, and sleep solutions using pressure sensitive mats
to aid in mattresses selection [
99
]. Their technology has been implemented in a variety of medical
studies, with a particular focus of managing pressure ulcers [
100
103
]. Pressure Profile Systems
continue to sell capacitive pressure sensors as of mid-2016 for a variety of applications, including
gloves, robotics, pressure mats, and medical applications [
104
]. LG have recently announced the
release of a flexible textile sensor based on capacitive technology [
105
]. It is difficult to ascertain the
exact make-up of many of these sensors and they may not be true E-textiles. Certainly, Peterson et al.
stated that the XSENSOR
®
devices use proprietary capacitive technology, and described the sensor as
a flexible thin pad [100].
The simpler textile switch also found its way into commercial products. In 2006 an intelligent
push-button system was described in a patent [
106
]. Beyond this a patent in 2006 [
107
], followed
by an article [
108
] described a fully integrated textile switch. Other patents by France Telecom
(Now Orange S.A., Paris, France)) [
109
], Daimler Chrysler (Auburn Hills, MI, USA) [
110
] and Sentrix
(New York, NY, USA) [111] also describe alternative textile switch technologies.
The Burton Amp snowboarding jacket saw integrated textile switches on the arm of the jacket used
to control an Apple iPod in 2002 [
112
]. Nike + iPod Sports Kit was another example of Apple engaging
with sports apparel companies to create an E-textile device. In this case a sensor was incorporated into
the shoe which communicated with an Apple product (such as an iPhone) or other Nike wearables
(such as the Nike + Sportband) to track activity [
113
]. The recent Google and Levi’s Jacquard jacket
also included textile switches [114].
6. Textile Energy Solutions
By the early 2000s the first patent for textile-based energy harvesting appeared in the form of
a mechanical generator scavenging energy through motion [
115
]. A paper by Qin et al. in 2007
described a technique for energy scavenging using piezoelectric zinc oxide nanowires grown radially
around textile fibers [
116
]; this being one of the earlier examples of energy scavenging within textiles.
The further development of energy storage and scavenging within textiles became a key area
of interest in the 2010s as the viability of many of E-textile products and concepts are dependent on
a suitable power supply. Existing textile energy scavenging (or energy harvesting) devices exploit
either thermoelectrics, kinetics, or photovoltaics. Each system possesses different advantages or
disadvantages, with many modern systems incorporated into textiles providing flexibility but lacking
other textile properties such as bend or shear. In all cases the harvested power was minimal, with
the most promising generators capable of producing sustained power on the order of milliwatts.
Both thermoelectric and kinetic systems draw energy from the wearer while photovoltaic energy
Fibers 2018,6, 34 7 of 15
harvesting draws energy from light sources, such as the sun. Photovoltaics have also shown significant
promise concerning the power that can be generated (~30 mW/m2) [117].
The use of carbon-nano tube based systems have gained significant popularity for both
energy harvesting and storage [
117
121
]. For an energy storage device the textile can be used as
a substrate for flexible films, or a carbon nano-tube infused film can be used to produce yarns [
120
].
Storage technology is either capacitive (normally supercapacitors) or chemical in nature. The use of
carbon nano-tubes has caused some worry due to safety concerns [
122
], which would possibly impede
future commercialization.
Another popular storage method has seen flexible, solid electrolyte-based batteries [
123
] woven
into a garment as thin strips, however at present these batteries are still large relative to a normal yarn
(width = 10 mm).
Triboelectric nano-generators are also viewed as a potential source of energy for wearables given
their very small size, high peak power densities, and good energy conversion efficiencies [
124
].
Triboelectric generators convert mechanical energy and therefore could be powered by human
motion or vibration. Despite high energy densities, the converted energy has a small current
and the generators energy output over time is unpredictable, requiring complex supporting power
management electronics. Cui et al. have demonstrated a cloth-based triboelectric generator where
frictional forces between the forearm of the wearer and their body was used to generate energy [
125
].
Comprehensive reviews of energy harvesting and storage in textiles are available elsewhere [
14
,
120
].
7. Communication Devices
A textile-based antenna fabricated from polymer (polypyrrole) strips has been described in the
literature [126]. Two conference papers from 2010 have also describe conformable antennas for space
suits [
127
,
128
]. The production of flexible embroidered antennas has been reported as suitable for
megahertz frequency communications [
129
,
130
]. This type of antenna is highly sensitive and has been
employed for unilateral magnetic resonance measurements [131].
Incorporating radio frequency identification (commonly known as RFID) tags into textiles has also
been investigated by a number of entities. Textilma were granted a patent describing an RFID module
textile tag [
132
]. Another patent described a method of attaching RFID chips to a textile substrate [
133
]
however, full integration within yarns was not proposed. A patent from 2007 also described a RFID
device, this time focusing on clothing [
134
]. In 2005 a patent described the incorporation of RFID
devices within epoxy resin for use in laundries [
135
]. A patent from 2010 described an RFID tag with
integrated antenna [
136
] whilst another patent from the same year described a method of incorporating
a RFID device into a textile tag [137].
8. Illumination
Interest in illuminated textiles continued into the mid-2000s with a patent from Daimler Chrysler
in 2005 describing a textile-based lighting system for automotive applications [
138
]. A patent
described creating a flat-panel video display by weaving electronically conductive fibers, such as
dielectrics [
139
]. This led to patents being filed for other textile-based flexible displays in later
years [
140
,
141
]. Other patents granted described a lighting system that used light leakage from optical
fibers in specific locations [142] to create illumination.
A patent from 2011 described a method of producing an illuminated pattern using light conducting
fibres [
143
]. Another illuminated textile using optical fibres was described in a patent from the same
year [144]. The company Sensing Tex Sl have used optical fibers to illuminate textiles [145].
In contrast, Philips have produced illuminated textiles using LED technology [
146
]. Philips have
previously patented a flexible electro-optic filament [
147
]. There are a variety of companies that produce
illuminated clothing for fashion applications, as well as use in performance (i.e. theatre), these include
Cutecircuit [
148
] and LUcentury [
149
] which create garments by sewing LEDs onto existing clothing.
Given advances in LED technology, reducing their size, LEDs can easily be incorporated into yarns
Fibers 2018,6, 34 8 of 15
using functional electronic yarns technology, and subsequently into garments [
75
]. Electroluminescent
yarn was also developed on 2010 [
150
] with the technology fully described in a 2012 paper [
151
].
Another form of lighting used for E-textiles was by attaching lasers to a garment, as shown by Bono
in 2009 [
152
]. This technology is not practical for a mass produced garment for a variety of reasons
including cost and the weight of the final garment.
9. Market Trends
According to IMS Research (Wellingborough, UK), 14 million wearable devices were shipped
in 2011 [
153
]. This clear market coupled with the significant scientific advances in E-textiles led to
a proliferation of devices entering the market in the early 2010’s, and an increased interest in the
technology from academia. More recently the Fung Global Retail and Technology report on wearables
in 2016 [
154
] identified a significant increase in the wearable market between 2015 and 2016, a 18.4%
climb to $28.7 billion. This is far higher than the predictions of the IMS, expecting that the revenue for
wearable technology would be $6 billion in 2016. Forbes currently predict that the wearable market
will reach $34 billion by 2020 [
155
]. It is of interest to note that the Fung report also states that the
top wearable brands of 2016 were Fitbit, Xiaomi, and Apple based on the number of units shipped:
These company’s products are not textile based. The principal wearable device sold by each company
are smart watches. It is unclear whether the growing market for wearables will become more focused
on textile-based devices in the coming years, but the advantages offered, such as comfort to the wearer,
will likely be an influential factor. The current market for E-textiles generates sales of around $100
million per year, with some sources predicting a $5 billion market by 2027 [156].
Current commercially available E-textiles include soft textile switches produced by International
Fashion Machines (Seattle, WA, USA) [
157
] and systems for incorporating wires into clothing by the
Technology Enabled Clothing [
158
]. Additionally, Fibretronic [
159
] have created a varied range of
products including (but not limited to) flexible switches, textile cables for signal or power transport,
and textile sensors, however as of 2018 it is unclear whether they are still trading. As discussed earlier
some sportswear E-textile products are no longer available, presumably due to poor market demand.
An important thing to note is that a significant number of website sources have been using in this review,
particularly regarding commercial products, as information was not available from other sources.
This is another possible indicator of poor uptake of certain products.
10. Potential Future Developments
While this review is focused on the history and evolution of E-textiles, it is of interest to consider
the direction that E-textile research will take in upcoming years. Originally, the vision of those
working in the field of E-textiles was to incorporate all of the required electronic systems within
the textile. More recently however some claim that the best approach is to use mobile phones as
an interface [
160
]; which has been aided in part by the substantial advancement in mobile phone
technology in recent years. Others claim that this approach is a temporary diversion and there are
many advantages for fully embedded systems, and that as developments progress, the mobile phone
itself will be integrated into textiles. A complete integration of the electronics may also be unfavorable
for sustainability reasons as it makes the electronics more difficult to remove at the end of the life of
a product [161].
It is expected that there will be a far greater uptake of wearable electronics when battery technology
is improved or alternative energy sources, such as energy scavenging, become more viable. This is of
particular importance to E-textiles over wearables more generally, as most conventional power sources
are not well suited to textile integration due to size, inflexibility, and lack of washability. The reductions
in size and cost of components will promote further development and uptake. A review paper from
2012 discussed the subject [
162
] and a BBC news item outlined on-going UK research in the area [
163
].
Ultimately, the adoption of E-textiles will depend on the cost. This will reduce with material costs
and improvements to the manufacturing processes. It is also possible that developments in graphene
Fibers 2018,6, 34 9 of 15
technology will be improve the potential of what can be achieved with electronic textiles. Many major
companies including Samsung, Nokia, and IBM have made significant investments into graphene
technology [
164
]. There is the potential that graphene’s physical properties, including its strength and
electrical conductivity, will allow it to replace silicon in many devices, possibly by the late 2020s after the
technology has matured. In addition, work on carbon nanotubes is beginning to show some promise,
especially for energy-based applications (such as energy harvesting and scavenging) [
117
,
119
121
].
Both technologies offer potential for further miniaturization of embedded electronics.
With an enhancement of how much can be fit within a textile, and suitable energy solutions,
E-textiles could move towards true wearable computing, with the textile managing and processing data
on its own depending upon requirements. The decreasing size of microprocessors makes embedding
this kind of intelligence within a textile likely in the immediate future.
11. Conclusions
This review of the literature has clearly shown that the three pathways of integrating electronics
into textiles have been applied in different ways. The methods of integrating electronics offer different
advantages and disadvantages. The first generation E-textiles will always interfere with the textile
properties of a garment, even thin film devices (while flexible), will not possess the shear properties
of a normal textile. The second generation textiles may retain a textile feel but are limited in their
applications; such as the creation of electronic pathways, and electrode-based sensing.
The third generation of E-textiles, where electronics are contained within the yarn structure,
do not interfere with the textile properties of a fabric. As this technology is principally limited by the
size of the incorporated electronics (i.e., the electronic chip dimensions) the potential of this area will
grow as smaller electronic chips become available.
While the history of E-textiles has shown the development of new techniques to integrate
electronics within a textile it is likely that the existing three methods will remain in use into the
future. The attachment of electronics onto a garment is still common, in particular for illuminated
textiles, despite this technology first being demonstrated in 1883.
Author Contributions:
T.H.-R., C.C. and T.D. located the reference material used in the review. T.H.-R. and T.D.
reviewed all of the reference material used in this review. T.H.-R. prepared the final manuscript.
Conflicts of Interest: The authors declare no conflict of interest.
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... Moreover, the prepared spandex contains many functional groups that can provide reaction points for combining dyestuffs and conductive materials. However, studies on the adsorption mechanism of graphene oxide, carbon nanotubes and other conductive materials containing certain anions on dyeable spandex are still limited [11][12][13][14][15][16][17][18]. The present study used anionic dye instead of anionic conductive material to investigate the adsorption performance of dyeable spandex. ...
... If dyeing thermodynamics conforms to the Langmuir adsorption isotherm, Formulas (7) to (11) are used to calculate thermodynamic parameters. Additionally, if it conforms to the Freundlich model, Formulas (9) to (12) are used to calculate thermodynamic parameters. ...
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... A wearable device is a smart device worn on the body for information and communication that can exchange continuously in real-time. Information can include the user's biometric information, such as movement, heartbeat, respiration, and surrounding environment information (e.g., temperature, humidity, and harmful factors) [1][2][3][4][5][6]. Wearable technologies can be versatile and meet system requirements across domains because of the various sensors and actuators embedded in wearable devices. ...
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Interface pressure is a key risk factor in the development of pressure ulcers. Visual feedback of continuous interface pressure between the body and support surface could inform clinicians on repositioning strategies and play a key role in an overall strategy for the prevention and management of pressure ulcers. A parallel two-group randomized controlled clinical trial will be conducted to study the effect of continuous pressure imaging on reducing interface pressure and on the incidence of pressure ulcers in vulnerable hospital patients. A total of 678 eligible consenting inpatients at risk of pressure ulcer development in a tertiary acute care institution will be randomly allocated to either having the ForeSite PT™ system with the liquid-crystal display monitor turned on to provide visual feedback to the clinicians while also collecting continuous interface pressure data (intervention group) or to having the ForeSite PT™ system with monitor turned off (that is, not providing visual feedback) but still collecting continuous interface pressure data (control group), in a ratio of 1:1. Continuous interface pressure data will be collected in both groups for 3 days (72 h). Data collection will continue until discharge for a subset of approximately 60 patients. The primary outcome will be the differences in the two groups’ interface pressure analysis. Interface pressure readings will be collected through hourly samplings of continuous interface pressure recordings. Secondary outcomes will be the differences between the two groups in pressure-related skin and soft tissue changes in areas at risk of pressure ulcer (obtained at baseline within 24 h of admission) and on the third day of the trial or at discharge and perceptions of the intervention by patients and clinicians (obtained on the third day or at discharge). This will be the first randomized controlled trial to investigate the effect of visual feedback with continuous interface pressure of vulnerable hospital patients across different care settings, and the association between interface pressure and development of pressure-related skin and soft tissue changes. The results could provide important information to guide clinical practice in the prevention and management of pressure ulcers. Trials registration ClinicalTrials.gov NCT02325388 (date of registration: 24 December 2014).
Chapter
As the world becomes more connected, our attention is increasingly divided. Clothing and accessories, when chosen carefully, can provide relief and assistance. For example, by adding more function to an outfit, you can consolidate the number of objects you need and make yourself more efficient when mobile. The ability to access e-mail or schedule an appointment on the go opens up new possibilities for where and how you can work. This chapter looks at the evolution of some of the earliest wearable technologies and the role they have played in fashion, technology, and society.
Patent
A “Wearable Electromyography-Based Controller” includes a plurality of Electromyography (EMG) sensors and provides a wired or wireless human-computer interface (HCI) for interacting with computing systems and attached devices via electrical signals generated by specific movement of the user's muscles. Following initial automated self-calibration and positional localization processes, measurement and interpretation of muscle generated electrical signals is accomplished by sampling signals from the EMG sensors of the Wearable Electromyography-Based Controller. In operation, the Wearable Electromyography-Based Controller is donned by the user and placed into a coarsely approximate position on the surface of the user's skin. Automated cues or instructions are then provided to the user for fine-tuning placement of the Wearable Electromyography-Based Controller. Examples of Wearable Electromyography-Based Controllers include articles of manufacture, such as an armband, wristwatch, or article of clothing having a plurality of integrated EMG-based sensor nodes and associated electronics.
Book
The "Handbook of Smart Textiles" aims to provide a comprehensive overview in the field of smart textile describing the state of the art in the research sector as well as the well-established techniques applied in industries. The handbook is planned to cover from fundamental theories, experimental techniques, characterization methods, as well as real applications with successful commercialized examples. The book is structured in a way in which it is appropriate for graduate students, PhD candidates, and professionals in diverse scientific and engineering communities devoted to relevant fields, including textile engineering, chemistry, bioengineering, material engineering, mechanical engineering, electrical engineering. The book will also provide a solid reference for industrial players who look for innovative technologies as well as environmental, safety concerns for the development of smart textile related products. © Springer Science+Business Media Singapore 2015. All rights reserved.
Book
The integration of electronics into textiles and clothing has opened up an array of functions beyond those of conventional textiles. These novel materials are beginning to find applications in commercial products, in fields such as communication, healthcare, protection and wearable technology. Electronic Textiles: Smart Fabrics and Wearable Technology opens with an initiation to the area from the editor, Tilak Dias. Part One introduces conductive fibres, carbon nano-tubes and polymer yarns. Part Two discusses techniques for integrating textiles and electronics, including the design of textile-based sensors and actuators, and energy harvesting methods. Finally, Part Three covers a range of electronic textile applications, from wearable electronics to technical textiles featuring expert chapters on embroidered antennas for communication systems and wearable sensors for athletes. • Comprehensive overview of conductive fibres, yarns and fabrics for electronic textiles • Expert analysis of textile-based sensors design, integration of micro-electronics with yarns and photovoltaic energy harvesting for intelligent textiles • Detailed coverage of applications in electronic textiles, including werable sensors for athletes, embroidered antennas for communication and electronic textiles for military personnel.
Article
Aim: The aim of this pilot study was to better inform clinical decisions to prevent pediatric occipital pressure ulcers with quantitative data to choose an appropriate reactive support surface. Materials: A commercially available capacitive pressure mapping system (XSENSOR, X3 Medical Seat System, Calgary, Canada) was used to evaluate a standard pediatric mattress and four commercially available pressure-redistributing support surfaces. Methods: The pressure mapping system was validated for use in the pediatric population through studies on sensitivity, accuracy, creep, and repeatability. Then, a pilot pressure mapping study on healthy children under 6 years old (n = 22) was performed to determine interface pressure and pressure distribution between the occipital region of the skull and each surface: standard mattress, gel, foam, air and fluidized. Results: The sensor was adequate to measure pressure generated by pediatric occipital loading, with 0.5-9% error in accuracy in the 25-95 mmHg range. The air surface had the lowest mean interface pressure (p < .005) and lowest peak pressure index (PPI), defined as the peak pressure averaged over four sensels, (p < .005). Mean interface pressure for mattress, foam, fluidized, gel, and air materials were 24.8 ± 4.42, 24.1 ± 1.89, 19.4 ± 3.25, 17.9 ± 3.10, and 14.2 ± 1.41 mmHg, respectively. The air surface also had the most homogenous pressure distribution, with the highest mean to PPI ratio (p < .005) and relatively high contact area compared to the other surfaces (p < .005). Conclusion: The air surface was the most effective pressure-redistributing material for pediatric occipital pressure as it had the lowest interface pressure and a homogeneous pressure distribution. This implies effective envelopment of the bony prominence of the occiput and increasing contact area to decrease peak pressure points.