| Present interest in nanotechnologies is rooted in biomimetics. Ultimately, the natural world can only be understood by analysis at the molecular level. This means working on the nanometre scale of dimensions. As Chris Byrne reminded the conference, this level of analysis is necessary to understand the remarkable properties of wool fibres. | |
Nanotechnological Approaches to Fibre Modification, Fibre Application and
Fibre Production
Philip Brown, Clemson University, USA.
This overview paper demonstrated how many of the functionalities for conventional
fibres are being achieved by modification, new fabrication techniques and materials
design. Self-cleaning wettable fabrics have been stimulated by the lotus leaf.
Textile fibres can be modified via hybrid polymer nanolayers and further modified
to achieve ultrahydrophobicity and the desired self cleaning. The desert beetle
Stenocara uses
hydrophilic protrusions on its carapace to gather moisture, which then flows
into hydrophobic channels which guide the water movements. This has stimulated
thoughts on fog
harvesting and improved efficiencies for air conditioning systems using
surfaces engineered in a similar way. Another area of research involves photonic
films and fibres, including synthetic opal. Like real opals, synthetic
opals are composed on ordered assemblies of nanoparticles and possess no
intrinsic color, but react with the light around them. Like the colors associated
with an oil slick on water, opals possess an internal structure that capture
the light and preferentially filters out some colors, leading to their well-known
iridescence. Application areas here include optical strain gauges, novel visual
effects, and very low loss light guides. A biological stimulus for some of this
work comes from butterfly
wings: the microstructure of the colourless scales gives a diffraction effect
yielding a variety of shimmering colours.
Two papers were concerned with carbon nanotubes. This area of research has been stimulated by the C60 buckminster fullerene (named after the architect of the geodesic structure, Buckminster Fuller). The original discovery was of a ball-shaped structure, but the two hemispheres can be extended by additional carbon rings (to make C70, C80, C90, etc). If this process is continued, a hollow molecular tube is formed.
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C60 buckminster fullerene
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A carbon nanotube viewed from the side.
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Fibrous Assemblies of Carbon Nanotubes
Alan Windle, University of Cambridge, UK
The processing and properties of carbon nanotubes was described, noting that
diameters of about 1 nm are obtained for molecular fibres (single-walled) and
5-10 nm for multi-walled nanotubes (compare ~10,000 nm for carbon fibres). The
fibres are strong, stiff and electrically conductive. Their properties can be
modified - for example, to make them semiconducting. A process of spinning carbon
nanotubes directly into fibres has recently been developed at Cambridge University.
This has been published: "Direct Spinning of Carbon Nanotube Fibers from
Chemical Vapor Deposition Synthesis", Ya-Li Li, Ian A. Kinloch, and Alan
H. Windle, Science, 9 April 2004; 304: 276-278.
The possibilities of developing this material as a high performance fibre or
as non-woven mats were discussed.
Carbon Nanotube- and Nanofibre-reinforced Polymer Fibres
Milo Shaffer, Imperial College, UK
Due to the remarkable properties observed for individual, perfect, nanotubes,
there is considerable interest in using
nanotubes and nanofibres as reinforcing agents in polymer composites. The challenge
has been to exploit these properties in real macroscopic materials. Whilst some
encouraging results have been obtained, significant improvements over conventional
fillers have proved elusive, for a number of reasons. It has become clear that
issues of dispersion, alignment, and stress transfer are crucial, and particularly
problematic at this size scale. In addition, it is necessary to consider the
type and quality of nanotubes used. A wide variety of synthesis methods have
been developed, yielding nanotubes of different size, aspect ratio, crystallinity,
crystalline orientation, purity, entanglement and straightness. All these factors
affect the processing and properties of the resulting composites. It is not
yet clear what the ‘ideal’ carbon nanotube would be, and the answer
may vary with matrix and application. This research is concerned with the production
of nanofibre-reinforced polymer fibres and looking at the issue of optimisation
of the properties of the composite.
Nanoparticle-loaded Polymer sensors and actuators for electronic textiles
Danilo De Rossi, University of Pisa.
A major Framework 6 project has been commenced on the development of e-textiles
for health, sporting and medical monitoring. This requires the extensive use
of sensors linked to a body suit. Numerous avenues have been explored: strain
gauges made of a conducting Lycra yarn built into knitted fabrics, sensors that
can detect the electrical activity of muscles and electrocardiogram signals.
Carbon nanotubes have been explored, and an elastomeric runner that swells in
an electric field.
| Source of illustration: KNITTED BIOCLOTHES FOR CARDIOPULMONARY MONITORING. R. Paradiso, A Gemignani, E, P. Scilingo and D. De Rossi. 25th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 17 - 21 September 2003. |
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This is clearly a very ambitious and challenging project. In response to a question on sensors, it was said that the current materials used for sensors do not last longer than 6 hours. The search is underway for more robust materials with the right properties. The Framework 6 project is known as WEALTHY.
Multifunctional Nanocomposites: Novel materials and potential textile applications
Steve Bull, University of Newcastle.
Nanotechnology is characterised by having dimensions in the 1-100 nm range.
Products are already available, mainly at the upper end of the scale. Examples
are thin films for glass and nanoparticles. The Intel chip has nanotubes. The
surface of computer hard drives may have a nano-coating for protection. Nanocomposites
have a 3D structure and will seek to have numerous advantageous properties.
Without multifunctional composites, cost will result in the use of traditional
materials. A review of the nanotechnology roadblocks was made: materials (including
health & safety issues), processing and cost.
Nanotechnologies for coatings and structuring of textiles
Thomas Stegmaier, ITV Denkendorf, Germany.
This paper was an overview of nanotechnology interests of the ITV
Institute of Textile Technology and Process Engineering Denkendorf. The
four topics identified were:
| The Lotus-Effect surface finish is modelled after the Lotus flower that exhibits self-cleansing behaviour when the flowers are washed clean by the morning dew. This nanotechnology application is based on a surface coating that is now commercial and used under licence. BASF first introduced the product in February 2004. Using a similar principle, a super-hydrophobic surface has been developed for medical textiles to avoid staining with blood. |  |
How medical devices can use nanotechnology and technical textiles
Jim McLaughlin, University of Ulster.
This was also an overview paper, with special reference to existing research
in Ulster. This has recently received a boost with the opening of the Nanotechnology
Research Institute. See also here.
Surface modification, nanoparticle incorporation into various polymers and sensor
technology within garments were discussed. Application areas of interest were
primarily in medical textiles.
Preparation of nanocellulosic fibres
Bogumil Laszkiewicz, Institute of Natural
Fibres, Poland.
Polymeric nanofibres can be produced using the technique of electrospinning.
The work reported has sought to extend the technique to produce cellulosic fibres.
Roadmapping of UK Nanotextiles
Chris Byrne, DTI Technical Textiles Project Coordinator
In this short presentation, roadmapping was described as the identification
and mapping of technology priorities
from a market/end-user perspective. To do this, a programme of consultation
workshops was outlined. DTI and EU initiatives relevant to nanotechnologies
were highlighted.
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Prepared May 2004