Researchers develop passive heating for eyeglasses

With the new patent-pending coating, the smallest amounts of gold are evaporated in a vacuum onto glass or other surfaces. What is special about the new coating is that it selectively absorbs solar radiation, explains the university.

“Our coating absorbs a large part of the infrared radiation and therefore heats up – up to eight degrees Celsius,” explains ETH PhD student Iwan Hächler, who played a key role in driving the development. Radiation in the visible range, on the other hand, does pass through. This is why the coating is transparent.

It works in the same way as a rear window defroster in a car: the glass is heated, preventing moisture from condensing on it. However, unlike the rear window, the new coating passively heats up and requires no additional energy when the sun is shining.

Wafer-thin and flexible
The coating itself is only ten nanometers thin and flexible. The gold consists of two layers of titanium dioxide, which, due to their light-refractive properties, increase the efficiency of heat generation and at the same time protect the gold layer from wear like a varnish.

Incidentally, only small amounts of the expensive metal are needed for the coating. ETH emphasizes that gold leaf is about twelve times thicker. Nevertheless, the researchers now want to investigate whether other metals are just as suitable as gold. In addition to glasses and car windows, this anti-fog principle could then be used wherever something needs to be heated and at the same time transparent, such as building windows, mirrors or optical sensors.

Versatile
According to Hächler, you don’t have to worry about a car or building heating up in the summer: “The window covering absorbs infrared rays from the sun, which specifically heat up the window and the radiation no longer reaches the interior of the car or building. As a result, the interior heats up even less than without the coating.”