Knitting with nanotubes

As if pulling threads from a silkworm’s cocoon, researchers in China have drawn fine yarns of carbon nanotubes from a reservoir of the microscopic carbon cylinders.

The resulting nanotube yarns, which can reach lengths of more than 30 centimeters, might eventually be woven into super-strong materials such as bullet-stopping fabrics, suggest Kaili Jiang, Qunqing Li, and Shoushan Fan of the Nanotechnology Research Center at Tsinghua University in Beijing. Carbon nanotubes are hollow tubes of carbon atoms just nanometers in diameter. Despite their size, they’re incredibly strong, and they hold promise for future generations of microelectronic chips.

The scientists stumbled upon their discovery while trying to pull nanotubes from an array. Instead of removing a bundle, the researchers reeled out a continuous length of nanotube yarn. The component threads are each several hundred nanometers wide. Weak forces called van der Waals interactions hold the threads together end-to-end.

The researchers suggest in the Oct. 24 Nature that a carbon nanotube array just 1 square centimeter in area can make about 10 meters of yarn.

Unlike other methods of making threads from nanotubes, the new one doesn’t require a solvent or some other additive, so the yarn contains pure nanotubes, and after heating, may maintain its superlative mechanical, thermal, and electrical properties, the researchers say (SN: 12/16/00, p. 398). In one experiment, the researchers formed the yarn into a lightbulb filament and found that its strength and conductivity increased after it heated up.

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