Self-cleaning wool and silk developed using nanotechnology

Good news for those who hate washing socks, are worried about hygiene or resent spending money on dry cleaning: self cleaning forms of wool and silk have been developed with the help of nanotechnology.

Wool socks, skirts and silk ties may soon clean themselves of smells and stains in the sunshine, researchers in Australia and China suggest.

The secret is a nano particle coating, one already used to keep windows clear, that could lead to "self-cleaning" versions of wool and silk fabrics.

Wool and silk, which are composed of natural proteins called keratins, are among the most prized and widely used fabrics in the clothing industry. However, they are difficult to keep clean and are easily damaged by conventional cleaning agents.

In the new study, scheduled for publication in the journal Chemistry of Materials, Dr Walid Daoud of Monash University, Victoria, Australia, and colleagues prepared wool fabrics with and without a nanoparticle coating - particles around five nanometres across (five billionths of a metre) composed of anatase titanium dioxide, a substance already used as a pigment that is known to break down and destroy contaminants upon exposure to sunlight.

"The self-cleaning technology in our work uses titanium dioxide photocatalyst that when triggered by light, it decomposes dirt, stains, harmful microorganisms and so on," says Dr Daoud.

The researchers then stained the fabric samples with red wine. After 20 hours of exposure to simulated sunlight, the coated fabric showed almost no signs of the red stain, whereas the untreated fabric remained deeply stained, the researchers say.

The coating, which is non-toxic, can be permanently bonded to the fibre and does not alter its texture and feel, they note, so a silk tie would still feel silky.

The tricky part of the research was finding a way to bind the keratin to the titanium dioxide, he says. "Applying a ceramic inorganic material to organic fibres, in particular keratin protein fibres such as wool, silk, hemp, and spider silk, remained a challenge."

After a chemical reaction to "activate" the surface of the fibres, the team found it could make the titanium dioxide crystals stick.

As for when self-cleaning socks could be on the market, Dr Daoud tells The Telegraph: "It is anticipated that as soon as the technology receives the approval technically and economically, you will then be able to see the product in the market. Currently, industrial testing and mill trials of this patent-pending technology are being conducted."

He adds: "I believe that self-cleaning property will become a standard feature of future textile and other commonly used materials to maintain hygiene and prevent the spreading of pathogenic infection. Particularly since pathogenic microorganisms can survive on textile surfaces for up to three months.

"Self-cleaning technology can also help in reducing the consumption of chemicals, such as detergents and dry-cleaning solvents, water, and energy."

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