Clothes usually get dirtier as you wear them, but in the future taking your t-shirt out of the drawer might actually clean it. Engineers at two Chinese universities have developed a type of cotton that is able to clean itself in response to sunlight.

The research, published in the Applied Materials and Interfaces Journal, builds on the use of titanium dioxide nanoparticles as a way of removing pollutants. The compound is being used in an increasing number of products because of its self-cleaning properties including stay-clean kitchen tiles, auto-clearing windows and even toothpaste.

Previously the use of titanium dioxide had been limited because the super-hydrophillic (or ‘water-loving’) form of the compound, which displaces dirt with water molecules, could only be ‘excited’ under ultra-violet light.

Now the technology has been perfected to work under visible wavelengths of light and included in cotton fabric by engineers at Shanghai Jiao Tong University and the Hubei University for Nationalities in China. The improvement came from the development of an alcohol-based nanoparticle compound of titanium dioxide and nitrogen which was then mixed with an acid neutraliser commonly used in dyes.

With the addition of silver iodide particles to boost the reaction, the resulting clear mixture can provide a coating for fabrics, with the advantages of being inexpensive, non-toxic and, of course, self-cleaning.

The team’s results have been very encouraging, in the experiment more than two-thirds of a stain placed on a piece of fabric had disappeared after two hours of exposure to light. The enhancement is also thought to be an enduring one, with the research indicating no loss of function following repeated dyeing or after washing and drying.

Titanium dioxide also has applications in sunscreen, toothpaste and the lines on sports fields, owing to its function as a bright white pigment. It is also known to break down pollutants from the air and has been used in paints. It is a material we are very likely to see a lot more of in the future.

Further information

Read the research in the Journal of Applied Materials and Interfaces

BBC News article on self-cleaning cotton

BBC News article on 'smog-eating' materials