Scientists discover mist opportunity

Scientists have cracked a problem that popular opinion suggests they suffer from most: steamed-up spectacles.

The solution, they found, lies in nanotechnology, the science of the vanishingly small. By applying an ultra-thin coating of particles to sheets of glass and other transparent surfaces, scientists at Massachusetts Institute of Technology made them permanently fog-proof.

Glasses steam up and car windscreens fog over when they are cold and meet warm, moist air, making thousands of tiny droplets of water condense on to the surface. The droplets scatter light as it passes through them, producing the misty, blurred effect.

The coating, a thin sandwich of transparent plastic and layers of silica particles too small to be seen with the naked eye, works by attracting water more strongly than the glass does. This flattens each of the water droplets, smearing them over the surface in a see-through layer.

"The coating basically causes water that hits the surfaces to develop a sustained sheeting effect, and that prevents fogging," said Michael Rubner, a materials scientist who led the research.

Dr Rubner, who announced the work at a meeting of the American Chemical Society in Washington DC yesterday, said the coatings could be used on spectacles, ski goggles, car windscreens and even bathroom mirrors. "Our coatings have the potential to provide the first permanent solution to the fogging problem."

They might find more bizarre applications. By patterning solid surfaces with the coating, Dr Rubner hopes to produce water-attracting channels that recreate a trick perfected by the Namib desert beetle. It uses inclined channels on its back to condense low-lying fog which trickles forward as drinking water.

Two car manufacturers and the US military have expressed a strong interest in the fog-free coating, which should be available commercially within five years, he said.

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