Heatable Film Could Eliminate Foggy, Frozen Windows in Wintertime
A heatable, virtually transparent film made out of indium tin oxide surrounds this glass tube.
CREDIT: Fraunhofer Institute
Researchers have found a new way to make heatable, nearly transparent films that could eliminate fogged or frozen vehicle windows in wintertime.
These prototype films prevent condensation, which is when water vapor in the air cools and returns to a liquid state. Scientists at Germany's Fraunhofer Institute, the organization behind the new research, will demo the films at glasstec, an industry trade fair in Düsseldorf late next month.
Current films produced using tin oxide suffer mechanical and optical drawbacks, according to the Fraunhofer Institute. Cracks can form as a result of excessive temperatures , a problem encountered during the glass bending process.
As a result, tin-oxide films have only limited industrial applications. "Our new film is extremely resilient," said Bernd Szyszka from Fraunhofer Institute. "Temperatures up to 1,652 degrees Fahrenheit (900 degrees Celsius) are no problem, and even if you bend it aggressively – the film remains intact."
The coating can therefore also be used in large industrial plants where transparent protective heaters are often required to monitor the process chain safely.
The surface films are conductive – and therefore heatable – and provide another advantage: the low emitting properties of the outer film ensure the window cools down much more slowly, preventing condensation and remaining dry and ice-free.
"Our coating system is based on nanocrystalline indium tin oxide," said Szyszka. "This material doesn’t just have outstanding optical and electrical properties; it is also mechanically and chemically much more stable than tin oxide."
While the advantages of such a coating have been known for many years, it is only now that these kinds of film systems can be manufactured less expensively for a much larger range of applications, the Fraunhofer Institute stated.
Not only is the film easy to heat – without any of the annoying wires commonly found in typical rear-heated window – the film boasts an optical transmission ratio of over 80 percent. The coating is also corrosion- and scratch-resistant, all of which could be good news for those frustrated by having to scrape windows clean of ice every wintry morning.