How to keep windows clear using gold and sunlight.As the northern hemisphere’s winter arrives, the problem of fogged-up car windscreens becomes more pressing for drivers.When humid air hits a surface colder than it is, the water vapour it carries condenses onto that surface as myriad tiny droplets.These scatter light at random.The result, if the surface is transparent, looks to a human eye like fog.Depending on what is fogged, be it windows, spectacle lenses or windscreens, that can be a curiosity, a nuisance or a serious hazard.Antimisting sprays are one way to deal with such fogging.But they need frequent reapplication.Another approach is to embed within the thing to be demisted a set of electrically powered heating wires.That works for a car’s rear window but not (because of the visual distraction created) for its front windscreen.Nor does it suit the windows of buildings or the lenses of spectacles to be demisted in this way.Iwan Hachler and Dimos Poulikakos of the Swiss Federal Institute of Technology in Zurich have, however, come up with another way of warming something up to stop condensation forming.Their new material, which they describe in Nature Nanotechnology, is a coating ten nanometres thick.
