ETH developing non-fogging glasses

Researchers from the Swiss Federal Institute of Technology in Zurich (ETH) have developed an ultrathin, gold-based transparent coating that prevents glass and other surfaces from steaming up. It can convert sunlight into heat, as ETH explains in a video. This allows the lenses in a pair of spectacles, for example, to be heated by up to 8 degrees Celsius, with the result that they no longer fog up during the winter or when worn over face masks. However, this technology could also be used for mirrors, car windscreens and optical lenses, further details of which can be found in a press release issued by ETH. Moreover, such little gold is required that the material costs are still low. For comparison, gold leaf is about twelve times thicker than the gold layer used in this nanocoating, which is only 10 nanometers thick.

In contrast to the coating first presented three years ago, this updated version offers several advantages. On the one hand, it is made up of fewer layers and is therefore significantly thinner, more transparent and flexible. On the other hand, it should be more efficient and transparent because it selectively absorbs infrared radiation. ETH has submitted a patent application for this technology.

The gold layer is sandwiched between two protective layers of titanium oxide, an electrically insulating material. Because of its light refraction properties, it increases the efficacy of heat generation. The individual gold clusters are all in slight contact with one another. As a result, the gold layer is conductive and can also be electrically heated in the absence of sunlight.

ETH doctoral student Iwan Hächler allays fears that building interiors would become hotter if the coating were to be used for windows. The reason that this would not happen is that sun’s infrared rays are absorbed by the pane coating. “As a result, the interior heats up even less than it would without the coating”, Hächler explains in the press release.