Glass that's anti-reflective and self-cleaning

Researchers at the University of Cambridge have come up with a coating that is not just anti-reflective, but self-cleaning as well. 

Reflections on an outdoor ad

Manufacturers have been making anti-reflective coatings modelled on moth eyes for some time, but once dirt builds up on them, the coatings tend to become useless. 

A press release from the University of Cambridge notes that using nanoparticles to such coatings can make them self-cleaning. Professor Ulli Steiner and colleagues from the Cavendish Laboratory came up with a strategy to make layers of plastic with very well-defined small pores, similar to moth eyes. But by making the pores larger than they are in most other types of moth eye coatings, they were able to incorporate titanium dioxide nanocrystals into the structure.

The nanocrystals are photocatalytic — when light falls on them, they start to break down the dirt clogging the pores, until all that is left is carbon dioxide, and water which evaporates off the surface, rendering the material self-cleaning.

In early tests of the material, the titanium dioxide nanoparticles were able to break down all of the oils contained in a fingerprint within 90 minutes. The coating is capable of breaking down most of the standard hydrocarbons that clog most porous antireflective coatings, the university said. 
 
The team is looking at applications in building glass and solar cells, as much of the sunlight solar cells are meant to capture and convert to energy simply bounces off the surface, and current antireflective coatings become easily clogged with dirt. “When generating energy from solar cells, you have to fight for every percentage gain in efficiency,” said Professor Steiner. 

Details of the coatings were described in the journal Nano Letters.