Efstratios Mitridis, another doctoral student in Poulikakos’s group, explains what makes the new surface coating so special: “Normally, it’s dark surfaces that absorb light and convert it into heat,” he says, “but we’ve created a transparent surface that has the same effect.”
Better than anti-fog sprays
Condensation occurs on a surface whenever there is a sudden drop in temperature or increase in humidity, forming tiny droplets of water that disperse incident light in different directions in much the same way as atmospheric fog. As an alternative to using heat to prevent fogging, susceptible surfaces can be coated with hydrophilic agents. Because they attract water, these agents ensure that the condensation forms an even thin film of liquid over the surface rather than separate droplets. Anti-fog sprays for glasses usually work on this principle.
Now, tests have shown that when exposed to sunlight, fogged surfaces coated with gold nanoparticles and titanium oxide clear four times faster than surfaces treated with a normal anti-fog agent. “Spray treatments often lose their effect after a while because the anti-fog film dries up or becomes unevenly distributed,” Walker says. “A durable coating like ours lasts much longer than a spray treatment, which you have to apply virtually on a daily basis,” he adds.
The ETH scientists are now planning to bring their new method to market, in collaboration with a partner from industry. “We’re looking to refine our already robust coating to ensure it lasts for years, and we want to take the technology from lab scale to industry scale,” Walker says. Their coating has a huge range of potential applications, including car windshields and rear-view mirrors as well as ski goggles and diving masks.
