10.05.10

Moths inspire anti-glare surface

AUTHOR: Inavate

A new nanocoating inspired by moths will reduce glare on screens and solve problems that can plague the DOOH market.

The Fraunhofer Institute for Mechanics of Materials IWM developed the coating that is claimed to ensure a perfectly non-reflecting view on displays. Moths’ eyes, which do not reflect light in order to hide from predators, provided a prototype for the development.

On a moth’s eye tiny protuberances, smaller than the wavelength of light, form a periodic structure on the surface. This nanostructure creates a gentle transition between the refractive indices of the air and the cornea. As a result, the reflection of light is reduced and the moth remains undetected.

Research scientists at the Fraunhofer Institute for Mechanics of Materials IWM in Freiburg have adopted this artifice and adapted it to a range of different applications. On eyeglasses, cell phone displays, fitting or panel covers, transparent surfaces are generally only useful if they allow viewing without light reflecting back.

Whereas conventional methods apply the anti-reflective coating in a separate step after production, the Fraunhofer scientists have found a way of reducing light reflection during actual manufacture of the part or component: “We have modified conventional injection moulding in such a way that the desired nanostructure is imparted to the surface during the process,” explained Dr. Frank Burmeister, project manager at the IWM.

For this the researchers have developed a hard material coating which reproduces the optically effective surface structure. “We use this to coat the moulding tools,” said Burmeister. “When the viscous polymer melt is injected into the mould, the nanostructures are transferred directly to the component.”

Because no second process step is required, manufacturers achieve an enormous cost saving and also increase efficiency. “Normally the component would have to undergo an additional separate process to apply the anti-reflex coating,” Burmeister adds.

Normal plexiglass and some anti-reflex coatings are particularly sensitive, but the scientists are producing wipe-resistant and scratch-proof surfaces. For this purpose the injection mould is additionally flooded with an ultra-thin organic substance made of polyurethane. Burmeister: “The substance runs into every crevice and hardens, like a two-component adhesive.”

The result is an extremely thin nanocoating of polyurethane on which the optically effective surface structures, which are just one ten-thousandth of a millimetre thick, are also reproduced.