

Video: Self-washing fibres Video: Self-washing fibres

(Image: Altrendo Images/Getty) This scanning electron micrograph shows that carbon nanotube yarns containing 88 per cent silicon dioxide powder by weight are strong enough to be knotted (Image: Science/AAAS)

One of the biggest hurdles in the way of “smart clothing” may finally have been jumped. Nanotechnologists have developed conducting fabrics that can survive a washing machine.


Garment makers would like to introduce novel materials into textiles to create conducting paths that, say, connect sports performance sensors or your music player to your phone.

“But until now, such multifunctional applications have been limited by the ability to spin important materials into yarns and make sure they stay there even after washing,” says Ray Baughman of the Alan G. MacDiarmid NanoTech Institute at the University of Texas in Dallas.

To solve this problem, his team set about making a yarn that could be peppered with “guest” particles of interest – titanium dioxide to create self-cleaning fabrics, for instance – and hold onto them through a hot dunking in detergent. What better way to do that, they thought, than to wrap the particles up in a tightly scrolled web?

Nanoforestry

When a commercially produced “forest” of multiwalled carbon nanotubes is cut into with a razor, drawing the blade out slowly pulls out an exquisitely fine web of nanotubes held together by intramolecular van der Waals forces.

“As you pull, nanotubes stick to the blade, and that pulls the next nanotube, and that one the next, and so on,” says Baughman. “So you end up with a sheet, a web of nanotubes. And once you have drawn out a sheet, you can twist it into a yarn.”

But the researchers don’t spin straight away: first they need to introduce the guest particles they want to trap within their yarn. To do this, they take their nanotube web – which is 1 centimetre wide and just 50 nanometres thick – and place it on a filter paper soaked in a solution of the guest material. Or the solution can be deposited as an aerosol from an electrostatic paint gun.

Once the particle-populated nanoweb is dry, it is clamped at one end while the other is twisted by a spinning magnet, of the type used to stir fluids in the lab (see video above). The result: a yarn that holds onto the guest particles within it and can be woven alongside woollen and cotton threads for clothing manufacture.

Appliance of science

Would the guest material be released and lost in the washing machine, though? To find out, Baugham ran tests in a Maytag washing machine at standard 40 °C washing temperatures – but also in a three-hour soak at 80 °C. In neither case did they find guest material to have been depleted.

They plan more tests, however, because different physical stresses that are used in spinning change the way the yarn is “scrolled up” – and that may affect guest particle retention.

The Texan team have now made yarns containing titanium dioxide, various conductors and even “high-temperature” superconductors such as magnesium diboride.

Jobs for yarns

Why a superconducting yarn? Because this is not all about clothes: there could be many engineering applications for smart yarns in superconducting linear motors, batteries, supercapacitors and hydrogen storage systems.

Theoretically the thin conducting skins that could be woven with this material could also have applications in stealth aircraft, as the material would be an ultralight radio-frequency radiation absorber that could foil radar. Baugham wouldn’t comment on whether that is a target application, though he says aerospace firms are interested.

The team have lodged an international patent filing on the idea and are now working with what Baugham describes as “an agency” on the most immediate applications for it.

Journal reference: Science, DOI: 10.1126/science.1195912