Carbon nanotubes could be used to create structures that mimic artificial muscles, according to new research from the Rensselaer Polytechnic Institute in New York.

The boffins said that carbon nanotubes are well suited for this purpose because they can withstand repeated stress and still retain their structural integrity.

"The idea was to show how fatigue affects nanotube structures over the lifetime of a device that incorporates carbon nanotubes," said Victor Pushparaj, a senior research specialist in the Department of Materials Science and Engineering at Rensselaer.

"Even when exposed to high levels of stress, the nanotubes held up extremely well. The behaviour is reminiscent of the mechanics of soft tissues, such as a shoulder muscle or stomach wall, which expand and contract millions of times over a human lifetime."

Pushparaj and his team created a free-standing, macroscopic, two-millimetre square block of carbon nanotubes, made up of millions of individual, vertically aligned multi-walled nanotubes.

The researchers then compressed the block between two steels plates in a vice-like machine more than 500,000 times.

Pushparaj's team recorded precisely how much force was required to compress the nanotube block down to about 25 per cent of its original height.

Even after 500,000 compressions, the block retained its original shape and mechanical properties along with its original electrical conductance.

The report, Fatigue Resistance of Aligned Carbon Nanotube Arrays Under Cyclic Compression, appears in the July issue of Nature Nanotechnology.