Against Water on Windows and Lenses

Photo: Water droplets

Researchers have been developing anti-fog technology for years, but each approach has its drawbacks. Some stores carry special anti-fog sprays that help reduce fogging on the inside of car windows, but the sprays must be constantly reapplied to remain effective. Therefore the team has developed a unique polymer coating — made of silica nanoparticles — that they say can create surfaces that never fog. The transparent coating can be applied to eyeglasses, camera lenses, ski goggles … even bathroom mirrors, they say.

"Our coatings have the potential to provide the first permanent solution to the fogging problem," says study leader Michael Rubner, Ph.D., a materials science researcher at MIT in Cambridge, Mass. "They remain stable over long periods, don’t require light to be activated and can be applied to virtually any surface." Coated glass appears clearer and allows more light to pass through than untreated glass while maintaining the same smooth texture, he says. The coatings consist of alternating layers of silica nanoparticles, which are basically tiny particles of glass, and a polymer called polyallylamine hydrochloride, both of which are relatively cheap to manufacture, Rubner says.

When fogging occurs, thousands of tiny water droplets condense on glass and other surfaces. The droplets scatter light in random patterns, causing the surfaces to become translucent or foggy. The new coating prevents this process from occurring, primarily through its super-hydrophilic, or water-loving, nature, Rubner says. The nanoparticles in the coating strongly attract the water droplets and force them to form much smaller contact angles with the surface. As a result, the droplets flatten and merge into a uniform, transparent sheet rather than forming countless individual light-scattering spheres.

COMPAMED.de; Source: American Chemical Society