Spinning Carbon Nanotubes into Electronic Yarns
Highly efficient electronic yarns that could be used for energy storage, conversion or harvesting, have been created by nanotechnologists at The University of Texas in Dallas. The yarns, which can be sewn into fabric and other textiles, could be used to turn our clothes into mobile accessories or solar cells.
As in textiles, where a yarn is spun from a web of wool, cotton or another material, the electronic yarns are spun from a web of carbon nanotubes that have been coated with a particular powder. The nanotube web acts as a host for the powder particles, which are what give the yarn its electronic properties. By using different powders as a coating for the nanotube web, each yarn has a different use, including superconductors, batteries and fuel cells.
The powder was stuck to the ultra-strong and ultra-lightweight host material made from a web of carbon nanotubes. The researchers created rows of the particles along the length of the web, so that when it was spun, the powder particles ran down in corridors through the yarn. This produces very high conductivity making it very efficient at transporting energy.
"That is a very interesting aspect of the nanoscale. Adhesion between particles and nanotubes can be very high because of the very high surface area of the nanotubes," said Ray Baughman, Director of the Nanotech Institute at the University of Texas.
The final product had in some cases a 95 weight per cent of the powder, meaning that almost all of the weight in the yarn was contributed by the particles that were stuck on to the nanotubes. This was because the carbon web was so lightweight.
Previous technology had not allowed for these powders to be spun efficiently, and often the only solution was to create a yarn and then bind the powder to the final product or merely incorporating it with the fibre surface. In this new method, the powder is incorporated at the first stage of spinning.
Baughman and his team used three different spiralling techniques to create the yarns known as Archimedean, Dual Archimedean and Fermat Spiralling, which all had slightly different properties. "These yarns are very highly flexible, which means that despite having 95 per cent powder within them they can be knitted, knotted or sewn. This flexibility is very important for their applications." The yarns were even durable enough to survive exposure to different solvents and several tumbles in a washing machine, with no loss of the powder within them.
Louise Ogden spoke to Ray Baughman from the Nanotech Institute in Dallas, Texas about his work on creating yarns from carbon nanotubes and powders...