Anyone who skis, wears glasses, uses a camera or drives a car is familiar with the problem: if you come into a humid environment from the cold, your eyewear, camera lens or windshield can quickly fog up. Researchers at ETH Zurich have now developed a new transparent material coating that greatly reduces this effect. Just a few nanometres thick, their durable coating is made of gold nanoparticles embedded in non-conductive titanium oxide.

“Our coating absorbs the infrared component of sunlight along with a small part of the visible sunlight and converts the light into heat,” explains Christopher Walker, a doctoral student in ETH Professor Dimos Poulikakos’s group and lead author of the study. This heats the surface up by 3 to 4 degrees Celsius. It is this difference in temperature that prevents fogging.

Passive heating

Heat is also the answer to the problem of fogging on car windows. Warm air from the in-vehicle heating system heats the front windscreen, while the rear window is fitted with a grid of electrical heating elements. But unlike these methods, the ETH researchers’ new coating works passively. Since the only energy source required is the sun, their coating is especially suitable for wearable items such as glasses and goggles.