A Hong Kong team has developed a self-cleaning cashmere that uses energy from the sun. The technology coats cashmere fibers with tiny particles that help break down bacteria, dirt and even coffee and wine stains. Within 24 hours of daylight exposure, red wine or coffee stains disappeared.

Researchers have applied a coating of the mineral anatase titanium dioxide to cotton and wool since 2002, but this is the first time the technology has been applied to cashmere, a fabric that is very expensive to clean. Retaining the softness of the fabric and also preventing damage to the delicate fibers from the oxidisation process was a huge challenge.

If commercialised, the process could lead to substantial savings on energy, water, washing liquids and dry cleaning chemicals. The price of the treatment would only increase the cost of production by one per cent or so. Washing and dry-cleaning do not remove the coating from the fibers. Anatase titanium dioxide is not on the list of materials restricted by the US.

However, questions remain. Sunlight is not available 24 hours a day. Direct sunlight may not always be available. Whether diffused sunlight will work is uncertain. There’s also a doubt whether sunlight would discolor the fabric.