Butterfly wings could hold key to developing clothes that change color on demand

Tiny crystal-like structures discovered in the wings of tropical butterflies could lead to color-changing clothing, according to scientists.
 
Physicists from Hong Kong discovered how subtle differences in the layers of butterfly wings create varied patterns of color, even among closely related species, The Daily Mail reports.

They claim that this process could be replicated and lead to materials being developed which can be 'tuned' to change color on demand.

The three butterflies studied by researchers from Hong Kong Baptist University all displayed what's called iridescence - a property of materials that change color depending on the viewing angle.

They included the Ulysses butterfly that appears to be a bluish green when seen from above and its cousin, Papilio peranthus, that looks more of a yellowish green.

The third butterfly, called the Emerald Swallowtail, is a deep green.

However, the color of all three butterflies switches to deep blue when seen from a different angle.

They discovered that each butterfly did so with different colors so the scientists examined a cross-section of each species' wing under a scanning electron microscope.

The wings were found to contain solid flat layers known as cuticles alternating with thin 'air' layers known as laminae.

The Ulysses butterfly, for example, was found to have seven cuticle layers while P. peranthus had eight.

The laminae also contain pillars of the cuticle material, which gives the wing a repeating crystal-like structure.

This structure is similar to a multi-layered mirror that reflects only certain wavelengths, or colors, of light.

It was from tiny differences in these crystals that the differences in colours arose.

'It all comes from the fact the wing structure has subtle differences between these three types of butterfly', said lead researcher Dr Kok Wai Cheah.

'It was very exciting to see how nature can create a nanostructure that's not easy to replicate by humans.'

He added the findings could lead to designer materials that could change color in a similar way, or appear to be made of different colors depending on the viewing angle.

The same article of clothing, for example, could reflect a subdued colour during the day, and a more ostentatious one at night.
'You would just tune your structure to produce the color you want,' said Cheah.