Nature wings it for 30 million years

The brilliant colours of a butterfly's wing are generated in the same way as the high-definition pictures of the trendiest plasma-screen TVs, scientists have found.

African swallowtail butterflies have used the principles of the latest light-emitting devices to generate the vivid colours of their wings, said Dr Peter Vukusic, a physicist at Exeter University.

A study of the microscopic properties of the butterfly's wing has found that, for 30 million years, swallowtails have manipulated light beams in ways that would tax the abilities of the best electronic engineers.

The wings are coated with an ultra-thin layer of molecules that form microscopic air spaces where fluorescent pigments absorb ultraviolet light and re-emit it as vivid patches of blues and greens.

The air spaces have a complex of multi-layered mirrors at the bottom to force light out through the top surface of the wings.

Further analysis, published in the journal Science, has found that the airspaces are arranged in such a precisely uniform manner that the fluorescent light is prevented from leaking out sideways, to make sure the colours are clear and bright.

Vukusic said that the butterfly has essentially invented a biological version of the light-emitting diode (LED) - a device for emitting light efficiently from where it is generated - many millions of years before they were developed by engineers.

"It's amazing that butterflies have evolved such sophisticated design features which can so exquisitely manipulate light and colour. Nature's design and engineering is truly inspirational," Vukusic said.

The wings of African swallowtails are coated in micro-scales, which are essentially regular air pockets within the stiff material that makes up the insect's external skeleton.

The fluorescent pigment within each space absorbs and re-emits light to produce the wing's colours, and the microscopic holes ensure that little light is lost from the airspace.

"The function of the micro-scales is identical to those in the LED," Vukusic said.

- INDEPENDENT