Cashmere is a fine quality wool whose delicate nature generally means a trip to the dry cleaner is required to deal with any stains on an article of clothing made from the material. But now a researcher at City University of Hong Kong (CityU) has developed a self-cleaning coating made up of nanoparticles that removes stains from cashmere by exposing the garment to light.

Developed by a team led by Dr Walid Daoud, Assistant Professor at CityU's School of Energy and Environment, the novel technology involves applying a coating of nano-sized photocatalysts to cashmere. When exposed to light for around 24 hours, these nanoparticles trigger an oxidation mechanism that breaks down any surface contamination, including stains, dirt and bacteria (and presumably red dots, too). This self-cleaning capability has a "long lasting, durable effect," says Dr Daoud.

Dr Daoud, who started off developing self-cleaning, protective materials in 2002 for cotton and later for wool, faced extra difficulty when turning his attention to cashmere, which he says "can be easily damaged" and "has poor resistance to oxidation, chemicals and high temperatures."

Another concern was any potentially damaging effects on human health the nanoparticle coatings may present in the event they should come off and be inhaled or absorbed. To address this, the CityU team says it has also developed a set of testing platforms and standard protocols to ascertain the performance and safety of the coatings.

"The project aims at delivering a set of testing systems and standard protocols, including a nano-coating emission chamber for testing stability, nanoparticle performance and safety of nano-coating fabrics under simulated wear, and conditions for safe and up to standard usage," Dr Daoud said.

"We have tested the performance and wash stability of the self-cleaning nano-coating textiles," added Dr Daoud. "Our preliminary study of the interaction of the nano-coatings with the nano-particles shows no harmful effect on cells indicating safety for practical application."

Daoud believes that these results will help smooth the way for the self-cleaning technology onto the market. He lists savings on energy, water and petroleum-derived chemicals used in the dry-cleaning process as potential advantages for the technology – along with savings on dry cleaning costs.