A RECORD-breaking fibre spun from carbon nanotubes has been yanked from the depths of an 鈥渆lastic smoke鈥�. The fibre, 100 metres long, is more than 300 times the length of the previous record holder.
Nanotubes are cylindrical molecules made up of a hexagonal arrangement of carbon atoms, like microscopic rolls of chicken wire. They conduct electricity better than copper, and because each tube is a single molecule they are very strong.
Engineers hope to exploit these properties on a larger scale by twisting nanotube fibres together into long threads. Possible applications include tough composites for aircraft fuselages, or stronger power cables.
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To create the nanotubes that make up their ultra-long fibres, Alan Windle and a team at the University of Cambridge injected ethanol into a fast-flowing stream of hydrogen gas, which they then heated to 1000 掳C. At that temperature, the pairs of carbon atoms from ethanol molecules combine to form nanotubes about 1 micrometre long.
The nanotubes float in the stream of hydrogen in an aerogel, a very low-density solid that forms as the carbon tubes become loosely linked to each other. Windle describes the aerogel as an elastic smoke. When a glass rod is poked into the aerogel, a few nanotubes adhere to it. Rotating the rod 鈥� like swirling candy floss or cotton candy with a stick 鈥� pulls on these, which in turn pull their neighbours, dragging out a continuous fibre of closely aligned nanotubes, Windle will report in Science (DOI: 10.1126/science.1094982).
Windle accepts that the properties of his record-breaking fibres are 鈥渞eally quite modest鈥�. While they are strong enough to weave into threads (see Picture), these are not yet any stronger than their conventional polyester equivalent.
Other experts are unimpressed, though. 鈥淪o they鈥檝e wound it on a reel. Big deal,鈥� says Malcolm Green, a fullerene chemist at the University of Oxford. 鈥淚f they can spin it and get a fibre that has immense strength, then they鈥檝e won the battle. But they haven鈥檛 done that.鈥�
