Moths’ eyes inspire novel nanocoating

Research scientists at the Fraunhofer Institute for Mechanics of Materials IWM in Freiburg have created a nanocoating that can be used to create non-reflecting displays and eyeglasses.

The scientists’ inspiration came from an unusual property found in moths’ eyes, whose surfaces are covered with a natural nanostructured film that eliminates reflections, allowing them to see well in the dark, without reflections to give their location away to predators.

Building on this idea, the Fraunhofer team has created a nanocoating that can be used to create non-reflecting displays and eyeglasses.

Whereas conventional methods apply anti-reflective coatings in a separate step after production, the Fraunhofer scientists developed a way of reducing light reflection during the 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,’ said Dr Frank Burmeister, project manager at the IWM.

To do this, the researchers developed a hard material coating that reproduces the optically effective surface structure.

’We use this to coat the moulding tools,’ said Burmeister. ’When a 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.’

What is more, while plexiglass and some anti-reflex coatings can be scratched easily, the new nanocoating can be used to produce wipe-resistant and scratch-proof surfaces. To do this, the injection mould is flooded with an ultra-thin organic substance made of polyurethane, which then 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.

Working in co-operation with industrial partners, the researchers now aim to develop components for the auto industry that are not only attractive to look at but also hard wearing and easy to clean.