The Elements of Innovation Discovered
The Elements of Innovation Discovered
Swiss researchers create gold coating that heats up in sunlight Metal Tech News – December 14, 2022
Despite wearing a facemask outside in the cold, the left lens of this individual's glasses (right side from the reader's perspective) is fog-free due to a gold nanocoating developed by scientists at ETH Zurich. The fogged right lens is uncoated.
Swiss researchers have developed a transparent gold nanocoating that vanquishes the perennial nemesis of glasses wearers – fogging.
Unlike traditional antifogging methods, which uses hydrophilic coatings that evenly spread condensation across the surface of the glass, the micro-thin gold layer developed by scientists at ETH Zurich harnesses sunlight to passively heat the lenses to prevent fog from forming in the first place. This works on the same principle as the heating elements put into car windows to prevent fogging but without the obtrusive element or the need for an external power source.
The golden layer does not harness the spectrums of sunlight we are most familiar with – the visible light and UV bands. Instead, it transforms infrared light, which accounts for half the energy in sunlight, into a passive heating system.
"Our coating absorbs a large proportion of the infrared radiation, which causes it to heat up – by up to 8 degrees Celsius (14 degrees Fahrenheit)," explains ETH doctoral student Iwan Hächler, who was a driving force behind the development.
While gold is practically synonymous with opulence and expense, it has the ideal properties – excellent electrical conductivity and pliability – for making a transparent nanocoating and does not contribute significantly to the cost due to the very small amount of this precious metal required.
The coating developed by the ETH team is made up of extremely thin clusters of gold sandwiched between two ultrathin layers of titanium oxide, an electrically insulating material. Titanium is also renowned for its durability, and the outside layer of titanium oxide selects the dual purpose of protecting the gold from wear.
This whole titanium oxide-gold "sandwich" is just 10 nanometers thick, which is about 12 times thinner than common gold leaf.
With gold being an excellent electrical conductor, the clusters only need to touch each other minimally, which is what allows the gold layer to conduct electricity.
In the absence of sunlight, this golden antifog layer could still be activated with electricity from a battery or other external source.
Beyond vanquishing the nemesis of glasses wearers, this invisible antifog layer could be applied to automobile windows, bathroom mirrors, building windows, optical sensors, or anywhere both heat and transparency is desired.
While having fog-free glass in your car or home would be great, the prospect of windows that generate extra heat during hot summer days is not. The ETH scientists, however, say their gold nanocoating would block radiant heat.
"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," Hächler explained.
ETH Zurich professors Dimos Poulikakos and Thomas Schutzius say the antifog gold nanocoating can be produced with vapor deposition under vacuum, a technique extensively used in manufacturing.
ETH Zurich has applied for a patent on the coating.
With more than 16 years of covering mining, Shane is renowned for his insights and and in-depth analysis of mining, mineral exploration and technology metals.
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