Smart Windows Clean Themselves, Save Energy

A revolutionary new type of smart window could cut window-cleaning costs in tall buildings while reducing heating bills and boosting worker productivity. Developed by University College London (UCL) with support from EPSRC, prototype samples confirm that the glass can deliver three key benefits:
Self-cleaning: The window is ultra-resistant to water, so rain hitting the outside forms spherical droplets that roll easily over the surface – picking up dirt, dust and other contaminants and carrying them away. This is due to the pencil-like, conical design of nanostructures engraved onto the glass, trapping air and ensuring only a tiny amount of water comes into contact with the surface.
 Energy-saving: The glass is coated with a very thin (5-10nm) film of window-cleaning of vanadium dioxide which during cold periods stops thermal radiation escaping and so prevents heat loss; during hot periods it prevents infrared radiation from the sun entering the building.
 Anti-glare: The design of the nanostructures also gives the windows the same anti-reflective properties found in the eyes of moths and other creatures that have evolved to hide from predators.

self cleaning windowA scanning electron miscroscope photograph shows the pyramid-like nanostructures engraved onto glass: at 200nm they are 100 times smaller than a human hair. Controlling the surface morphology at the nanoscale allows scientists to tailor how the glass interacts with liquids and light with high precision

This is the first time that a nanostructure has been combined with a thermochromic coating. The bio-inspired nanostructure amplifies the thermochromics properties of the coating and the net result is a self-cleaning, highly performing smart window, said Dr Ioannis Papakonstantinou of UCL. The UCL team calculate that the windows could result in a reduction in heating bills of up to 40 per cent.