Size is everything for nanotubes

For the first time, researchers have created a simplified method for making long, continuous strands of carbon nanotubes that are as much as eight inches in length.

Researchers from Rensselaer Polytechnic have created a simplified method for making long, continuous, hair-like strands of carbon nanotubes that are as much as eight inches in length.

This breakthrough is said to be a first step toward creating microcables for electrical devices or mechanically robust electrochemical actuators for artificial muscles.

The Rensselaer researchers and collaborators at Tsinghua University in Beijing found that chemical vapour deposition (CVD), a widely used technique to grow nanotubes, has a high yield of long strands when a sulphur-containing compound and hydrogen are added to the process.

Researchers have previously created nanotube fibres with more complex methods, but because CVD is commonly used to make nanotubes, it would be easily adaptable and more efficient for synthesising the long strands for practical applications.

This new method produced nanotubes that measured 20 centimetres, much longer than conventional nanotubes, said Pulickel Ajayan.

‘Carbon nanotubes are generally microns in length, which is not long enough for any practical purpose,’ said Ajayan, associate professor of materials science at Rensselaer Polytechnic Institute.

‘We have created strands with nearly aligned nanotubes that are as long as 20 centimetres. The nanotubes are well ordered in these structures and are self-assembled during the growth process, which means we don’t end up with an unusable lump that looks like cooked spaghetti,’ he added.

The process could also be an easier alternative to creating high-purity single-walled nanotube material in general, said Bingqing Wei, one of Ajayan’s current graduate students who came to Rensselaer from Tsinghua University.