(December 21, 2015)
* Birds generate
their colour using structure, not dyes and pigments
* The jay is able to
change the colour of its feathers along the equivalent of a single human hair
using a tuneable nanostructure
* This discovery may
lead to synthetic structural colour that could be made cheaply and used in
paints and clothes that will not fade like dyes and pigments.
Birds use sophisticated changes to the structure of their
feathers to create multi-coloured plumage, using a process that could pave the
way for the creation of paints and clothing colours that won’t fade over time.
Using X-ray scattering at the ESRF facility in France to
examine the blue and white feathers of the jay, researchers from the University
of Sheffield found that 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
material, exactly 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.