The butterfly effect

The coloured brilliance of butterfly wings is the inspiration for research into patterned films designed to more effectively protect bank notes and other documents from counterfeiters.

A Cambridge University physics department team led by Prof Ullrich Steiner plans to accurately mimic the complicated light effects produced by butterfly wings, which change colour and intensity depending on the angle from which they are viewed.

The project aims to produce thin, brightly-coloured films that would be impossible to forge.

Steiner said: ‘Our motivation is biomimetic. In nature, organisms such as butterflies produce brilliant colours — far more brilliant than is possible using just pigments. The appearance changes when looked at from different angles because the surface’s microstructure reacts with light in different ways.’

Steiner said butterflies’ wings use a complicated interplay of different physical effects to create a brightly-patterned appearance. The wings use different multilayered periodic patterns ranging from a micron to a few hundred nanometres in length. Often other optical elements, such as tiny micro-prisms, are used to scatter the light in a particular way.