Pilkington Glass has invented a window which can clean itself, and the special glass is up for a £50,000 innovation prize.
Pilkington Aciv uses two processes to clean itself. It absorbs ultra-violet light which causes a "photocatalytic" reaction which breaks down dirt on the glass. The coating is also "hydrophilic" so water forms a continuous sheet rather than individual drops - this rinses dirt off the window.
The glass coating is made of titanium dioxide, more often found in sunscreen and toothpaste. The coating is only 15 nanometres thick. It is slightly more expensive than normal glass and has a slight blue tint.
The coating will take up to a week to absorb enough UV light to start eating dirt on the window but once it is "charged up" it will work on overcast days too.
Pilkington recomends the glass be used where cleaning is difficult and the window, or conservatory or sky light, is exposed to sun and rain. If the windows do need cleaning simply hosing down with water should be enough.
The glass has made the short list for the MacRobert Award, given by the Royal Academy of Engineering. There are four finalists this year: Delphi Diesel Systems is on the list for a two valve fuel injector system which cuts emissions from diesel engines. IBM's Websphere MQ middleware which allows 40 different computer platforms talk to each other is still in the running. The final entry is a 3D imaging system from Sharp Labs - it is used on DoCoMo mobile phones and by airport security staff looking at X-ray images of luggage. The winner will be announced 10 June.