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Intelligent textiles
An electric yarn - Clothes that could report a wounded soldier
Dec 10th 2008
Economist.com
MANY science-fiction stories portray a time when warring generals monitor their forces on computer displays that are linked to electronic suits worn by each of their soldiers. Information about any injuries is sent to the command station immediately, so the generals will know that, say, Sergeant Johnson has a fractured ankle or that Corporal Caley has lost 1.2 litres of blood. Such a day may not be too far off. Researchers have been able to produce cotton fibres capable of detecting blood and of signalling its presence electrically.
Intelligent textiles have a lot of appeal. For both soldiers and doctors clothing that adapts to changing conditions could provide adjustable levels of protection from such things as microbes, chemicals and radiation. Commercial manufacturers see huge potential in clothes that glow, do not wrinkle or overcome body odour. Materials can already be made to do some of these things, but they are too bulky, rigid or complicated for practical use. So the aim is to manufacture a light material that can be easily woven but that is also highly durable and, in order to transmit information, capable of electrical conductivity.
A team of researchers led by Nicholas Kotov, a chemical engineer at the University of Michigan, has come up with a way in which this might be done by coating cotton threads with carbon nanotubes. These tubes are cylindrical carbon molecules with a unique honeycomb-like arrangement of atoms. They are regarded as among the most versatile nanomaterials available because of their mechanical strength and electrical properties.
Nanotube composites are often made into solid structures or sheets, although flexible versions, such as electrically conductive films and electronic inks, can be prepared from dilute nanotube solutions. Some electronic devices, such as field-emission displays in some flat panels, are made from nanotube yarns. But the weaving of these yarns, which may be only one-thousandth of a millimetre thick, is complicated and expensive. Scaling it up to create garments with electrical properties has not been considered practical.
However, Dr Kotov and his colleagues have reported in Nano Letters a simple process for coating standard cotton threads with carbon nanotubes. Being much thicker than nanotube yarns, such threads can be woven more easily. The researchers dispersed carbon nanotubes in a dilute solution of a mixture of Nafion, a commercial synthetic polymer, and ethanol. Then they repeatedly dipped cotton threads, 1.5mm in diameter, into the solution, letting them dry between each dip. This allowed the nanotubes to cover individual cotton strands and to adhere strongly to the surface of the cellulose fibres in the strands. The process also encouraged the nanotubes to arrange themselves along the axis of the cotton fibres, which increased electrical connectivity. After several dips, Dr Kotov found that the cotton threads became conductive enough even to be used as a wire to transmit a voltage to illuminate an LED light.
In a further test the researchers added to the dipping solution molecules of a material that react with human serum albumin, an essential component of human blood. Then they immersed more cotton threads. This time they ran an electrical current through the thread while exposing it to different concentrations of albumin. They found the threads were sensitive to albumin, and therefore capable of detecting the presence of blood and signalling it through their electrical conductivity. The researchers propose that such material could be used to detect bleeding and, if woven into military clothing, could help to monitor soldiers healthmuch as science fiction predicted.
An electric yarn - Clothes that could report a wounded soldier
Dec 10th 2008
Economist.com
MANY science-fiction stories portray a time when warring generals monitor their forces on computer displays that are linked to electronic suits worn by each of their soldiers. Information about any injuries is sent to the command station immediately, so the generals will know that, say, Sergeant Johnson has a fractured ankle or that Corporal Caley has lost 1.2 litres of blood. Such a day may not be too far off. Researchers have been able to produce cotton fibres capable of detecting blood and of signalling its presence electrically.
Intelligent textiles have a lot of appeal. For both soldiers and doctors clothing that adapts to changing conditions could provide adjustable levels of protection from such things as microbes, chemicals and radiation. Commercial manufacturers see huge potential in clothes that glow, do not wrinkle or overcome body odour. Materials can already be made to do some of these things, but they are too bulky, rigid or complicated for practical use. So the aim is to manufacture a light material that can be easily woven but that is also highly durable and, in order to transmit information, capable of electrical conductivity.
A team of researchers led by Nicholas Kotov, a chemical engineer at the University of Michigan, has come up with a way in which this might be done by coating cotton threads with carbon nanotubes. These tubes are cylindrical carbon molecules with a unique honeycomb-like arrangement of atoms. They are regarded as among the most versatile nanomaterials available because of their mechanical strength and electrical properties.
Nanotube composites are often made into solid structures or sheets, although flexible versions, such as electrically conductive films and electronic inks, can be prepared from dilute nanotube solutions. Some electronic devices, such as field-emission displays in some flat panels, are made from nanotube yarns. But the weaving of these yarns, which may be only one-thousandth of a millimetre thick, is complicated and expensive. Scaling it up to create garments with electrical properties has not been considered practical.
However, Dr Kotov and his colleagues have reported in Nano Letters a simple process for coating standard cotton threads with carbon nanotubes. Being much thicker than nanotube yarns, such threads can be woven more easily. The researchers dispersed carbon nanotubes in a dilute solution of a mixture of Nafion, a commercial synthetic polymer, and ethanol. Then they repeatedly dipped cotton threads, 1.5mm in diameter, into the solution, letting them dry between each dip. This allowed the nanotubes to cover individual cotton strands and to adhere strongly to the surface of the cellulose fibres in the strands. The process also encouraged the nanotubes to arrange themselves along the axis of the cotton fibres, which increased electrical connectivity. After several dips, Dr Kotov found that the cotton threads became conductive enough even to be used as a wire to transmit a voltage to illuminate an LED light.
In a further test the researchers added to the dipping solution molecules of a material that react with human serum albumin, an essential component of human blood. Then they immersed more cotton threads. This time they ran an electrical current through the thread while exposing it to different concentrations of albumin. They found the threads were sensitive to albumin, and therefore capable of detecting the presence of blood and signalling it through their electrical conductivity. The researchers propose that such material could be used to detect bleeding and, if woven into military clothing, could help to monitor soldiers healthmuch as science fiction predicted.
