While the idea of using nano-particles to enable textiles to repel dirt and 'self-clean' is not new, the uses to which this technology is being applied and enhanced are increasing almost daily. By Mark Rowe in London, and Gavin Blair in Tokyo look at some of the latest applications.

A number of products are currently being designed or put on the open market in Europe and the United States.

The Germany-based lifestyle brand Daniel Hechter, for instance, has launched a 'lotus flower' coat that causes water and dirt to drip off from a specially structured fabric surface. 

The dirt repellent coating uses the 'lotus effect,' whereby water beads and runs off the surface of lotus leaves as a result of wax pyramids which coat them.

The process works by reducing the surface area available on which dirt can gather by creating tiny nanoscale wax pyramids - the same principle that is in operation with lotus leaves.

Nanotechnology in use
Some of the biggest European and US fashion houses are also supplying garments into which nanotechnology is incorporated - notably being manufactured by the California-based nanotech fabric company Nano-Tex.

Hugo Boss, René Lezard and Paul Stuart are all using Nano-Tex's protective fabric treatment for high-end trousers, shirts and outdoor wear.

The key ingredient is a product marketed by Nano-Tex as 'Nano-Tex Resists Spills' - a treatment that repels liquids ranging from coffee and red wine to chocolate syrup and salad dressings while allowing the fabric to breathe.

The treatment is designed for use on cotton, polyester, wool, silk and rayon and works because the fabric is dipped in a solution of 'nanowhiskers' - tiny fibres of cotton that are 1/1000 of the width of a normal cotton fibre.

These fibres attach to the fabric create a cushion of air around the fabric, making it more wrinkle-resistant and causing liquids to bead up and roll off.

Meanwhile, the use of antimicrobial silver particles embedded into fabric fibres has this year been applied to sports underwear by the Germany-based company Jack Wolfskin.

The nanosilver particles significantly reduce the formation of bacteria and associated unpleasant odours.

While silver is highly toxic for microorganisms it has relatively low toxicity for human tissue cells; nanosilver particles have an extremely large relative surface area, increasing their contact with bacteria or fungi, and vastly improving its bactericidal and fungicidal effectiveness.

They are also efficient at transporting moisture, and wick sweat readily away from the body.

The company points out one limitation on the product: because nanosilver darkens any product with which it comes into contact, pure white underwear is not available.

Making waves in Japan
Textile cleaning innovation is also making waves in Japan, where the Shower Clean Suit from Konaka Group has been generating the kind of buzz about which marketing managers dream.

Having appeared in the year's first quarterly ranking of top consumer items in the Nikkei financial newspaper, the suit ranked highly again in the half-year round-up and is still getting a lot of attention in the media.

"There were suits that could be cleaned in the shower 20 years ago when I joined Konaka but they were made from polyester and lost their shape after washing," said Shigeyuki Tsuchiya from Konaka's PR department.

"Also polyester is not a good material for the humid Japanese summer, so they were never big-sellers."

The key to the new Shower Clean Suit is wool, which is mixed in an 83% wool/17% polyester material with water-soluble fibres.

Once the suit is stitched, it is washed, dissolving the fibres and leaving a lightweight material through which water and air can easily pass.

"We collaborated closely with [Australian-owned] The Woolmark Company for two years developing the Shower Clean Suit to get the material right. It's similar to human hair in the way it reacts to being washed," explained Tsuchiya.

Indeed, the final finish applied to the suits contains L-cysteine, an amino acid that occurs naturally in hair, nails and skin.

"The suit can be washed in a regular shower, at around 40 degrees, then it can be hung to dry in the bathroom and will be ready to wear without ironing," said Tsuchiya.

As well as the convenience factor, the lack of a need for dry cleaning or detergents is being marketed as environmentally friendly.  

"The suit is so popular at the moment that our factory in Beijing can't keep up with demand and we're expecting sales of around JPY2.2bn (US$20m) by year end," said Tsuchiya.

Men's Shower Clean Suits start at around US$475 and women's at around US$275.

The UK's John Pearse, a regular collaborator with Konaka, has teamed up with the business-wear specialists for two men's designs, while Kansai Yamamoto has provided two men's suits and one ladies' suit.

Meanwhile Exlan, which started selling its Selfclear self-cleaning nano-technology titanium oxide yarn for industrial uses in 2006, is finally seeing progress in the clothing arena.

"Up until now Selfclear has been used mainly for carpets, rugs and mats," said Testsuji Yoshida from the firm's Osaka head office.

"Our self-cleaning fibre business for clothes is just starting out and we've had trial orders for spring and summer sweaters this year."