This reporter in a foggy moment.

Some writers suffer from writer’s block. Not me. I have writer’s fog.

 Image courtesy of Amazon Kindle
Let me explain. It all started the other day when I had a positively Proustian moment after receiving a press release about a new anti-fog lens coating. As I started reading about the remarkable technology that makes this coating unique—more on that in a moment—the description began conjuring up long-ago memories. I thought of the famous scene from Marcel Proust’s “In Search of Lost Time” when he tastes the madeleine cookie, and it brings back vivid recollections of his childhood. Unlike Proust, this writer’s memories are a bit "foggy."

My mind first wandered to the Maine woods. I spent several summers there, attending a boy’s camp on Long Lake. Early mornings were chilly, and I could picture the ghostly fog that often hovered on the mirrored surface of the lake as it was slowly warmed by the sun. I used to imagine indigenous people paddling canoes, shrouded by a blanket of gray as they moved silently across the water.

From that placid lakeside I was transported to Kentucky’s bluegrass country. Looking out from high on a hilltop, I was mesmerized by the sound of Foggy Mountain Breakdown, the driving Flatt & Scruggs instrumental that helped cement Earl Scruggs’ reputation as a banjo virtuoso.

Next, I remembered another musical scene, this one from my teenage years. My friends and I were watching Foghat, the British blues-rock band, perform their latest bombastic hit on the late-night TV show, “Don Kirshner’s Rock Concert.”  I always thought the band’s name was ridiculous, even after learning it was a sly reference to smoking weed, as in, “I’ve got my foghat on.”

Then someone turned the channel, and I was watching “The Fog of War,” the 2003 Errol Morris documentary about the story of America as seen through the eyes of Robert McNamara, the former Secretary of Defense under President John F. Kennedy and President Lyndon B. Johnson.

Why am I sharing these memories with VMail Weekend readers? I haven’t the foggiest notion, except that this is how my free associating mind works. Forgive this lengthy digression. Now, about that new coating...

According to the press release I received, researchers from ETH Zurich have developed an ultrathin, gold-based transparent coating that is able to convert sunlight into heat. It can be applied to glass and other surfaces to prevent them from fogging. Applications for the new coating include car windshields and eyewear.

The researchers, led by ETH professors Dimos Poulikakos and Thomas Schutzius, point out that their coating is fabricated with methods which are used extensively in manufacturing. In a cleanroom and using vapor deposition under vacuum, minute amounts of gold are deposited onto the surface. ETH Zurich has applied for a patent on the coating. Click here to watch a video about it.

In winter, face masks can lead to fogged glasses. Here, the left lens (right from the reader’s perspective) has the new antifogging nanocoating. The other lens is uncoated. Image courtesy of ETH Zurich
What’s special about the new coating is that it absorbs solar radiation selectively. Half of the energy contained in sunlight resides in the infrared spectrum, the other half in the visible light and UV radiation spectrum.

“Our coating absorbs a large proportion of the infrared radiation, which causes it to heat up—by up to 8 degrees Celsius,” explained ETH doctoral student Iwan Hachler, who was a driving force behind the development. It absorbs only a minor fraction of the radiation in the visible range, which is the reason why the coating is transparent.

The new coating takes an approach that differs from conventional antifogging methods. Traditionally, surfaces are coated with water-attracting (hydrophilic) molecules, which results in an even spread of condensation. This is how antifog sprays work. But the new method instead heats the surface, thus preventing humidity-induced condensation from forming there in the first place.

It’s the same principle as is used for a car’s rear window. But, as Hachler points out, electric heating is inefficient and energy wasteful. In contrast, the new coating is heated passively and requires, during daytime, no additional energy source.

Poulikakos, Schutzius and their teams have been working on passively heated surface coatings for several years. Three years ago, the scientists published their first research paper on a gold coating that prevented transparent surfaces from fogging up. The coating they have now presented has many benefits over the first: It is made up of a single gold nanolayer and is significantly thinner, which makes it more transparent as well as pliable. Further, it is also more transparent and efficient because it absorbs infrared light more selectively.

Gold might be expensive, but the researchers emphasized that their coating requires so little that the material costs remain low. The coating comprises minuscule, extremely thin clusters of gold sandwiched between two ultrathin layers of titanium oxide, an electrically insulating material. 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 nanometers thick. By way of comparison, a common gold leaf is twelve times thicker.

Due to their refractive properties, the two outer layers of the coating increase the efficacy of the heating effect. The top layer of titanium oxide acts as finish that protects the gold layer from wear. This whole “sandwich” is just 10 nanometers thick. By way of comparison, a common gold leaf is twelve times thicker. Image courtesy of ETH Zurich

The individual gold clusters touch each other minimally, 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.

The researchers will now develop the coating further for other applications, the press release said. In the process, they will investigate whether other metals work just as well as gold. In addition to eyewear and windshields, this antifogging method could be used wherever objects must be both heated and transparent – such as windows, mirrors or optical sensors. However, there is no need to fear that this would cause a car or a building to heat up more in the summer. As ETH doctoral student Hachler explained, "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."

The research project received funding from the Swiss National Science Foundation.

I don’t know about you, but I can’t wait for this new coating to hit the market. My specs get steamy when I step from my warm house into the wintery cold, so I’m going for the gold.