Nature’s color techniques help explain why exactly the beautiful hues of birds don’t just fade away with age. The reason is that birds use structures instead of dyes to reveal their natural colors.
Avians seem to employ a complicated series of arrangements to show off their colorful plumage. The techniques used by birds include manipulation of the structure of their feathers instead of secretion of any dyes. This knowledge may be very helpful to humans later on in the creation of paints and emulsions for clothing that don’t become outdated.
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An x-ray scattering process was used to look at the blue and white feathers of a Blue Jay. Birds are not bird brains or so it seems. They employ a great many controls and techniques to show off their many hues. The problem with dyes and pigments is that they wear away over a period of years and decades.
But the feathers of these clever avians are able to change under duress so that they show transformations at the microlevel stage. The Jays recognize one another via these feathers and their coloration. Each barb of the Jay has a pattern rather as if a human hair had a rainbow of colors along its length. These make for the iridescence.
The Jay’s feathers run the gamut from blue to ultraviolet all the way to white. At a nanostructure level, the feathers show spongy keratin structures. This keratin is a protein also found in human hair and nails. The Jay bird is able to contract and swell the holes in this keratin.
This fixates the color it wants to show off to the world on the level of the feathers. When light strikes the Jay’s feathers, the holes determine how it is reflected and thus the color gets fixated. When the holes are larger, the color white is reflected. And when they are smaller, the color blue is reflected.
Were pigments to be made from nutritional elements in the bird’s diet, they would surely fade away with the passage of time. But thanks to the nanostructures, the colors remain throughout the life span of the Jay and other birds.
Nature has seen to it that the beautiful colors of the bird’s feathers remain as they are and don’t lose their luster and brightness. However, in humans pigments are used and so human hair gets gray with age. This avian strategy of permanent coloration may be used by science to create materials that don’t fade away as far as their hue is concerned.
Dr Andrew Parnell, from the University of Sheffield's Department of Physics and Astronomy said: "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."
Dr Parnell added: "This discovery means that in the future, we could create long-lasting coloured coatings and materials synthetically. 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.
"Current technology cannot make colour with this level of control and precision - we still use dyes and pigments. Now we've learnt how nature accomplishes it, we can start to develop new materials such as clothes or paints using these nanostructuring approaches. It would potentially mean that if we created a red jumper using this method, it would retain its colour and never fade in the wash."
Researcher Dr Daragh McLoughlin of AkzoNobel Decorative Paints Material Science Research Team added: "At AkzoNobel, the makers of Dulux paint, we aim to encourage and stimulate the innovation of more sustainable products that have eco-premium benefits. This exciting new insight may help us to find new ways of making paints that stay brighter and fresher-looking for longer, while also having a lower carbon footprint."
Dr Adam Washington from the University of Sheffield added: "The research also answers the longstanding conundrum of why non-iridescent structural greens are rare in nature. This is because to create the colour green, a very complex and narrow wavelength is needed, something that is hard to produce by manipulating this tuneable spongy structures. As a result, nature's way to get round this and create the colour green - an obvious camouflage colour - is to mix the structural blue like that of the Jay with a yellow pigment that absorbs some of the blue colour."
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The research findings are being published today, on 21 December 2015, in Nature Scientific Reports.