Self-cleaning cotton nanoparticle coating invented

Girl washing clothes by river Analysts say self-cleaning clothes could prove very popular in countries with humid climates

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Efforts to create self-cleaning cotton fabrics are bearing fruit in China.

Engineers have created a chemical coating that causes cotton materials to clean themselves of stains and remove odours when exposed to sunlight.

The researchers say the treatment is cheap, non-toxic and ecologically friendly.

Retail experts say the innovation could prove a hit with retailers thanks to a growing demand for "functional clothing".

The research was carried out by engineers at Shanghai Jiao Tong University and Hubei University for Nationalities, and is published in the latest issue of the Applied Materials and Interfaces journal.

The study focuses on titanium dioxide - a chemical known to be an "excellent catalyst in the degradation of organic pollutants".

The substance is already used in self-cleaning windows, odour-free socks and stay-clean kitchen and bathroom tiles.

Initial efforts to extend its use to cotton fabrics proved limiting because the substance's self-cleaning properties could only be "excited" under ultraviolet lights, making it impractical for everyday use.

Creating the coating

The team's breakthrough was to create a nanoparticle alcohol-based compound made up of titanium dioxide and nitrogen.

The mixture was added to triethylamine, an acid neutraliser commonly used in dyes. After being stirred for a 12 hours at room temperature, the liquid was heated at 100C (212F) for a further six hours.

The cotton fabrics were then immersed in the mixture before being squeezed dry, heated and immersed in hot clean water.

Finally the coated materials were treated with silver iodide particles, which aid light-based reactions.

To test the effectiveness of their invention, the engineers marked the fabrics with an orange dye stain and exposed them to the sun. After two hours in the light, the team said 71% of the stain had been removed - a "dramatic" improvement over previously trialled techniques.

Long-lasting

The experiment was repeated on the same cloth five times with no loss of activity - suggesting that the enhancement was stable. Washing and drying the material did not reduce its effectiveness.

Clothes industry experts said there should be huge interest in the process if it could be rolled-out on an industrial scale.

"This kind of functional clothing has already proved very popular, especially in Japan where the authorities ordered a crackdown on air conditioning use after March's earthquake caused power shortages," said Isabelle Cavill, a clothing analyst at Planet Retail.

"It is also likely to prove popular in other parts of Asia where the heat causes sweat problems."

Ms Cavill noted that the Japanese retailer Uniqlo has started promoting a "Silky Dry" range of clothing that promises to keep skin dry and odour-free thanks to special "high-tech processing neutralisers".

The firm also markets a "Heattech" line which "creates heat" to keep users warm.

Meanwhile, scientists at the University of Sheffield have been researching a fabric conditioner that helps purify the air around people wearing treated clothes.

"The main retailers to pick up on this latest innovation are likely to be those selling basicware," said Ms Cavill.

"In the West that could mean Wal-Mart or Marks and Spencer would want to invest in the Chinese technology to take advantage of functional clothing becoming more popular with shoppers."

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