eth zurich’s new antifogging coating turns light into heat
Following years of research, a team at ETH Zurich has developed an ultrathin, bendable, and transparent coating that prevents glass surfaces from fogging up thanks to a nanolayer of light-absorbing gold clusters. The experiment was carried out initially on eyewear and car windshields, with further applications underway.
Existing methods of managing humidity include fog sprays that evenly spread out condensation with a layer of hydrophilic molecules and electric heating to clear up a car’s rear windows. In contrast, this coating operates electricity-free by continuously absorbing sunlight and converting it into heat, thus preventing fog from building up in the first place.
the gold nanocoating was tested on eyewear | image via ETH Zurich
According to ETH Zurich (see more here), the new coating maintains its transparency at all times thanks to selective light absorption. Infrared radiations, which are invisible to the naked eye, are largely absorbed while visible light and UV radiations are mostly blocked out. Once radiations are soaked in, the thin layer begins warming up; its surface temperature can elevate by eight degrees celsius, effectively clearing out any possibility of condensation while wearing glasses or driving.
testing the antifogging coating on one lens | image © ETH Zurich
a 10 nanometer-thick ‘sandwich’
ETH Zurich researchers designed the coating by incoporating two ultra-thin titanium oxide layers separated by gold clusters. ‘Due to their refractive properties, these two outer layers increase the efficacy of the heating effect. Moreover, the top layer of titanium oxide acts as finish that protects the gold layer from wear.This whole ‘sandwich’ is just 10 nanometres thick. By way of comparison, a common gold leaf is twelve times thicker. The individual gold clusters touch each other minimaly, which is what allows the gold layer to just start conducting electricity. So in the absence of sunlight, it would still be possible to use electricity to heat the coating,’ writes ETH Zurich.
2019 testing on a transparent pane | image © ETH Zurich / Christopher Walker
the next steps
The project was led by ETH Professors Dimos Poulikakos and Thomas Schutzius who are looking into expanding applications of their nanocoating on other clear surfaces like windows, mirrors, and optical sensors. The team is also exploring the efficacy of other metal elements against the existing gold coating. ‘Gold might be expensive, but the researchers emphasise that their coating requires so little that the material costs remain low,’ notes the university.
When it comes to heating concerns during the summer period, doctoral studen Iwan Hächler reassures with the following: ‘The pane coating absorbs infrared rays from the sun, which specifically heats the pane and prevents the radiation from reaching the inside of the car or building. As a result, the interior heats up even less than it would without the coating.’
a bendable, ultra-thin layer | image via ETH Zurich
two titanium oxide layers separated by gold clusters | image © ETH Zurich