Researchers spin nanotubes into fibres

Materials scientists from the University of Pennsylvania and chemists from Rice University have reportedly manufactured fibres composed solely of single-walled carbon nanotubes.

Materials scientists from the University of Pennsylvania and chemists from Rice University have reportedly manufactured fibres composed solely of single-walled carbon nanotubes (SWNTs).

“Throughout the relatively brief history of carbon nanotube research, the creation of a usable nanotube fibre has been one of the ultimate goals,” said John E. Fischer, Professor of Materials Science and Engineering in Penn School of Engineering and Applied Sciences.

The main obstacle to creating a usable SWNT fibre comes from the very properties that make SWNTs so attractive. Individually, these carbon nanotubes are stronger than steel, conduct electricity better than copper and conduct heat better than diamond. Together, however, they tend to clump together in otherwise unusable bunches, largely impervious to the heating used to melt polymers and spin them into fibres.

The Rice technique of spinning SWNT fibres was inspired by the process used to create other modern super fibres such as Kevlar – the material used in bulletproof vests – and Zylon – a material twice as strong as Kevlar.

Using these conventional spinning techniques, the researchers extruded a dispersion of SWNTs at high concentration in a strong acid through a long hypodermic needle, allowing the resulting strand to coagulate before removing the acid.

As a result, the researchers transformed disorganised nanoscale materials into a continuous macroscale fibre. Each individual strand of the SWNT fibre is approximately 100 micrometres in diameter and contains about a million close-packed and aligned nanotubes.

Ultimately, CNL researchers believe pure nanotube fibers hold the promise of being 10 times stronger than Zylon.

“The early results are auspicious,” said Smalley, University Professor, the Gene and Norman Hackerman Professor of Chemistry and professor of physics at Rice.

“We’ve got no impurities, our densities are about 77% of what’s theoretically possible and we’re confident that the strength and conductance will improve as we refine the heat treatment, spinning and other elements of production.”