17 June 2003
17 June 2003
Carbon nanotube threads up to 100 metres have long created at the University of Texas, Dallas, and Trinity College, Dublin, with a toughness of three times greater than the toughest natural material, spider silk.
A cross section of the thread measures about 50 microns in diameter and contains hundreds of trillions of tiny carbon nanotubes per centimetre in length . 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 gel 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.""
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.