Electric blue

The iridescent blue that flashes from the wing of the Cherubina Emperor (Doxocopa cherubina) is such a brilliant shade it looks artificial. In fact it is very high-tech. While nature usually relies on pigments to paint colours, butterflies use nanotechnology.

The colour comes from the nanoscale structures, around a hundredth the width of a human hair, that line its wings. Like a sieve for light waves, they allow all the colours of light to pass through except for a pure wavelength of dazzling blue, far purer than that produced by a pigment, which typically reflects back a mix of colours. 

Engineers are copying the butterfly’s wing to create surfaces that sieve light with exquisite precision. 

Image courtesy of Dorling Kindersley/getty images

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Tiled Wings

Like ornate tiles on the roof of a Chinese temple, more than 100,000 overlapping scales form the surface of the wing of a Cherubina Emperor.  As early as the 1920s, scientists realised that the butterfly’s colour must come from the repeating pattern of grooves and ridges that decorates each scale. 

Unlike pigment molecules, which break down over time, structural colour never fades, says University of Oxford scientist Andrew Parker. Butterflies are not the only creatures to use it: Parker found fossilised beetles that sparkle as colourfully today as the day they died 45 million years ago. He and his colleagues are attempting to recreate these colours in fade-proof paints and fibres.

Image courtesy of Andrew R. Parker

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Looking Deeper

“Look deep into nature and then you will understand everything better,” Albert Einstein once said. In the 1950s electron microscopes opened a new window on the nanoworld and butterfly wings were one of the first things to go under the lens. At last the intricacy of the Cherubina Emperor’s wing structure was revealed. 

As Einstein predicted, looking deep shows us how nature creates “structural” colour. The sophisticated way these structures reflect and channel light is inspiring engineers to design new high-speed optical computers that use nimble photons of light in their circuits rather than bulky electrons.

Image courtesy of Andrew R. Parker

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Invisibility cloak

Few moths have the showy colours of butterflies but they still use nanotechnology tricks. The “windows” in the wings of this Clearwing Hawkmoth are as solid as the rest. Nanostructures guide light straight through without any reflection, giving the illusion of holes. By breaking up their wing shape in this way, the moths are less recognisable to predators.

ImageS courtesy of National Geographic /getty images

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Capturing light

Parker’s team has developed synthetic surfaces that mimic the moth’s anti-reflective trick, shown above. When coated on a solar panel, they cut reflection, increasing the panels light-capturing efficiency by 10%

ImageS courtesy of Andrew R. Parker