By David Cohen
Clothes woven with electrically conducting threads are a significant step closer with the creation of super-strong carbon nanotube fibres up to 100 metres long. They are stronger than any natural or synthetic organic fibre known.
Materials made from such strong threads could be used to make bullet-proof vests as light as a T-shirt. And their electrical properties could be harnessed to put microsensors into our clothes, measuring everything from temperature to heart rate.
The nanotube threads, created by Ray Baughman and colleagues at the University of Texas, Dallas, and Trinity College, Dublin, have a breaking strain of 570 Joules per gram. This is more than three times stronger than the toughest natural material, spider silk.
A cross section of the thread measures about 50 microns in diameter and contains tens of millions of tiny carbon nanotubes. To produce the threads, Baughman's team used a technique developed by Philippe Poulin, at CNRS in Bordeaux, France.
A spinning aqueous solution of carbon nanotubes and a surfactant is injected into pipe in which a solution of polyvinyl alcohol flows. The two solutions coagulate to form a rubber-like fibre, which is wound on to a mandrel.
In a second continuous process, the gel fibre is unwound, washed and dried to produce a solid polymer fibre of potentially unlimited length. The fibre contains 60 per cent carbon nanotubes bound together by polyvinyl alcohol. "We have not been able to find any material that is tougher than our carbon nanotube composite fibres," Baughman told New Scientist. "The fibre's toughness probably results from structural changes during stretching. This aligns the nanotubes in the fibre direction."
Poulin is impressed by the results: "They are the first people to produce fibres with these characteristics. The toughness of the thread is especially impressive."
The threads can also be used as capacitors to store very small electric charges and to power devices embedded in clothes. But improving the electrical properties is the key future challenges, says Poulin, by making them more conductive and more porous.
"These are the crucial properties for building sensors out of this material, and for making lighter fibres that are still highly conductive," he says.
Journal reference: Nature (vol 423, p 703)
NewScientist.com news service