O o d h e a d p u b L i s h I n g L i m I t e d

particular interest in the latter was the creation of a monomer that polymerised
onto wool to produce a dark green ICP (as opposed to the typical polypyrrole
grey-to-black coloration). Crosslinked pyrrole monomers were also synthesised:
α,ω -bis(3-pyrrolyl)alkanes (Foitzik et al., 2007b). These are effectively two
pyrrole molecules linked by a carbon chain, the length of which was varied.
Monomers of this type may result in crosslinked ICPs with improved
mechanical properties. The optimum chain length (taking into account
conductivity, yield and stability) was eight, and ICP deposition was achieved,
although the polymerisation was more difficult.
Deposition of ICPs other than polypyrrole and polyaniline is also possible,
although relatively uncommonly reported for wool. Thiophene variants have
been polymerised in situ on a range of fibre types including wool (Collie,
2007). Variants included reddish-brown 2,2,
′-bithiophene and blue 3,4-
ethylendioxythiophene (EDOT). An interesting aspect of this work was that
the scale structure of wool is not obscured by the ICP coating. While there
were some scale fragments and damage apparent, fabric tests showed no
reduction in strength or flexibility. Durability assessment in the same study
revealed much better durability of conductivity for ICPs based on thiophenes
than for polypyrrole when polymerised by the same technique.
A group of Indian researchers experimented with a simple electrochemical
© 2009 Woodhead Publishing Limited

---

Intelligent wool apparel
317
ICP deposition approach: Bhadani et al. (1993) simply wrapped wool, cotton
and silk yarns around the anode of an electrochemical cell, with pyrrole and
thiophene used as ICP precursors, and tetrabutylammonium hexachloro-
antimonate in 1,2-dichloroethane as the electrolyte. The ICP formed at the
anode, but largely accumulated on the yarn. Resistivity with pyrrole was in
the range 5–25 k
Ω cm, while for thiophene it was 7–65 MΩ cm. The research
was repeated with aniline as the precursor and p-toluenesulphonic acid as
the electrolyte (Bhadani et al., 1996). The effect of electrolysis time was
reported; the amount of ICP deposited increased fairly steadily with time,
while the resistivity decreased. Resistivity after five hours was 1.7, 1.6 and
5.2 k
Ω cm for cotton, silk and wool respectively, while the increase in weight
was 83%, 224% and 155% respectively. Similar experiments with pyrrole in
place of aniline demonstrated similar trends, but with higher overall
conductivity (Bhadani et al., 1997a,b).
13.4.2 Electronic textiles incorporating wool
Electronic textiles (or wearable electronics) are the fields of intelligent textiles
where most commercial outcomes have been achieved. Initially these have
been in the form of textile-based control panels (such as those from Softswitch
and Eleksen). Very few of these have been in wool products, primarily
because the initial products have been restricted to high-performance outerwear
garments, such as skiing or snowboarding jackets. The first product of this
type was the Burton Analog Clone jacket, with a Softswitch keypad integrated
into the sleeve, controlling a Sony MiniDisc portable audio player (Buechner
et al., 2002). In keeping with current trends the device now most commonly
controlled by these systems is the Apple iPod, including in the iPod-enabled
suit released in 2007 by Marks and Spencer in the United Kingdom (Eleksen,
2007). This system, utilising an Eleksen keypad, and manufactured for Marks
and Spencer by Bagir Ltd, integrated a five-button keypad inside the lapel of
the suit jacket. The jacket reportedly contained wool and elastane (Finch,
2007), and the keypad allowed control of the primary iPod functions without
needing to remove it from its internal storage pocket.
The other electronic textile application where wool has been utilised is in
electrically heated textiles. In a development supported by Australian Wool
Innovation, New Zealand-based Canesis Network Ltd (now part of AgResearch
Ltd) developed technologies for electrically heated wool socks (AWI, 2004a;
Jones  et al., 2007) and bedding (AWI, 2004b). In both cases the resistive
heating element was created from a blend of metallic fibre with Merino wool
to give an appropriate resistance level for heat emission with an applied
current. Higher conductivity non-wool yarns were used to provide the
connection to a power supply, which in the sock situation was to be based on
lightweight, high-capacity rechargeable batteries typically used in mobile
© 2009 Woodhead Publishing Limited

---

Advances in wool technology
318
phones. The heating ‘element’ was confined to a small region near the end of
the foot to maximise warming effect and battery lifetime.
New Zealand company Weratech have also developed a textile-based
electrical heating system. The Weratech system is also knitted, and the fabrics
are reportedly soft and flexible, and suitable for integration into a range of
garments, including gloves, footwear and coats (Tait, 2007). According to
their website (
www.weratech.com/Technology.html),
 the Weratech yarns use
conductive fibres blended with fine Merino wool, or other thermally stable
fibres, such as fire-retardant polyester or aramids. The fabrics rapidly heat
up to as high as 180
°C (although much lower temperatures would be appropriate
for apparel applications).
It must be noted that in neither of the application areas described above
does the inherent properties of wool have any particular role in making the
system an intelligent textile. Rather it is simply the substrate that the non-
fibre specific technology has been integrated into. They do, however, illustrate
that intelligent textiles are starting to permeate all areas of textiles, including
the very traditional wool market sectors of socks, knitwear and worsted
suits. In the case of the heated textile technologies, the concept of a heated
textile enhances wool’s image of being a warm, comfortable fibre to wear,
while in the unlikely event of a malfunction in the system, any overheating
or short-circuiting will not cause melting or burning of the textile thanks to
wool’s thermal stability and inherent flame-retardant behaviour.
13.4.3 Other applications
Specific applications for wool in the first two categories of intelligent textiles
defined in 
Section 13.2
 appear to be less common than in those areas discussed
above. In a 2005 article, Australian Wool Innovation was reported to be
examining applications for wool as a carrier for ‘smart chemicals’, with the
potential for wool-based ‘smart fibre dressings, for detecting infectious wounds,
to alert medical staff when a wound becomes infected’ (Anon, 2005). Such
a system might make use of the sensing capability of ICPs (discussed in
Section 13.4)
 to detect the biological agents produced in the wound
environment.
The only report of wool substrates being used in actuation systems appears
to be in work describing the binding of polyethylene glycols (PEGs) to a
range of fibrous substrates (Vigo, 1997). Wool is mentioned in passing in
this work, but no experimental results are provided. PEGs have a temperature
buffering effect thanks to phase change behaviour, and a shape-change
behaviour due to swelling when water is absorbed and desorbed. These
behaviours are imparted to the textile substrate to which the PEG is
bound.
© 2009 Woodhead Publishing Limited

---

Intelligent wool apparel
319