Gen-next fade-proof paints in the offing

Birds use sophisticated changes to the structure of their feathers to create multi-coloured plumage, according to a new study that could pave the way for paints and clothing colours that do not fade over time.
Using X-ray scattering to examine the blue and white feathers of the Jay, researchers from the University of Sheffield in UK found that the birds demonstrate a surprising level of control and sophistication in producing colours.
Instead of simply using dyes and pigments that would fade over time, the birds use well-controlled changes to the nanostructure to create their vividly coloured feathers - which are possibly used for Jays to recognise one another.

The Jay is able to pattern these different colours along an individual feather barb - the equivalent of having many different colours along a single human hair.
The Jay's feather, which goes from ultra violet in colour through to blue and into white, is made of a nanostructured spongy keratin, the same kind of material human hair and fingernails are made from.
The researchers found that the Jay is able to demonstrate amazing control over the size of the holes in this sponge-like structure and fix them at very particular sizes, determining the colour that we see reflected from the feather.

This is because when light hits the feather the size of these holes determines how the light is scattered and therefore the colour that is reflected.

As a result, larger holes mean a broader wavelength reflectance of light, which creates the colour white. Conversely, a smaller, more compact structure, results in the colour blue.
If the colours were formed using pigments created from the bird's diet, the feather colour would fade over time.
However, since nature has developed a way to create the colours through structural changes, any nanostructure will remain intact, explaining why birds never go grey as they age.

In contrast, humans rely on pigments to colour hair. As these are not produced to the same extent as we age, we consequently go grey.
"Conventional thought was that to control light using materials in this way we would need ultra precise and controlled structures with many different processing stages, but if nature can assemble this material 'on the wing', then we should be able to do it synthetically too," said Andrew Parnell, from the University of Sheffield.
"This discovery means that in the future, we could create long-lasting coloured coatings and materials synthetically," said Parnell.
"We have discovered it is the way in which it is formed and the control of this evolving nanostructure - by adjusting the size and density of the holes in the spongy like structure - that determines what colour is reflected," he said.

The study was published in the journal Nature Scientific Reports.