19 August 2005: Sticky tape pulls out a range of CNT applications
Nanotechnologists in the US and Australia have developed a simple process for creating metre-long sheets of carbon nanotubes (CNTs). The sheets are strong, transparent, flexible and able to conduct electricity. Potential applications range from heating car windows to building artificial muscle cells, the researchers claim.
The research team, led by Ray Baughman, professor of chemistry at the University of Texas at Dallas (UTD), used an adhesive strip to pull out the sheets from a thick horizontal mass of similar length multi-walled CNTs, known as a forest.
By pulling and twisting at the same time, the researchers pulled a 3m-long sheet from a 1cm-long forest consisting of trillions of 245Ám-high CNTs in under a minute. This is much faster than other methods for producing CNT sheets, such as filtering nanotubes dispersed in water, which can take many days.
The sheets are initially quite diffuse, with a density similar to aerogels, although they can still support millimetre-sized liquid droplets that are 50 000 times more massive than the supporting region of the sheet.
CNT sheets supporting droplets of orange juice, water and grape juice. (Science)
The density of the sheets can be increased by a factor of 360, by dipping them in ethanol and then allowing the ethanol to evaporate, which causes the sheets to shrink and thus increase in density. These modified sheets are as strong as sheets of a similar thickness made from ultra-high-strength steel.
Baughman and his team have already shown that these CNT sheets fluoresce when electricity is applied, which indicates that they could be used as organic light-emitting diodes. In addition, using microwave heating, the researchers found that the sheets could bond two polymer surfaces together while still retaining their electrical conductivity, which suggests that they could be used to make electrically-heated windows.
'Rarely is a processing advance so elegantly simple that rapid commercialisation seems possible and rarely does such an advance so quickly enable diverse application demonstrations,' said Baughman. His team is already working with academic and industrial researchers to develop and commercialise various aspects of the technology.
Medical researchers at UTD and Texas Scottish Rite Hospital for Children have found that healthy cells will grow on the CNT sheets, implying that they could be used as scaffolds for growing new tissue. Jon Evans
M Zhang et al, Science, 2005, 309, 1215