Scientists Seek to Stop Color-Fade
MONDAY, JANUARY 4, 2016
Why do colorful birds not turn gray as they age? Researchers at the University of Sheffield, South Yorkshire, U.K., say it comes down to the way color is created in the feathers.
Rather than depending on pigments and dyes, which naturally fade, the birds are able to control and change the nanostructures that create the vibrant colors of their feathers, the scientists say.
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| © iStock.com / ornitolog |
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Studying feathers of the Eurasian Jay, scientists at the University of Sheffield determined that the birds' plumage color is controlled at a nanostructure-level, rather than through pigments. |
Understanding how this mechanism works could lead to paints and other materials that won’t lose their color over time, the university announced in December.
The Science of Feather Color
“Bird feathers have proved particularly important in our understanding of structural colour,” the team wrote in a paper titled “Spatially modulated structural colour in bird feathers,” published Dec. 21 in Nature Scientific Reports.
Working with blue-and-white Eurasian Jay feathers, selected from the extensive collection of the Natural History Museum in London, the research team examined the plumes using X-ray scattering at the European Synchrotron Radiation Facility in France.
In the process, they discovered that the birds rely not on pigments created from diet, but by exhibiting a “surprising level of control and sophistication” in producing their colors.
According to the research, the jay is able to control the nanostructured spongy keratin material that makes up the feather, changing the sizes of the holes in the spongy structure and fixing them at very precise sizes. The variations in cavity size determine the color we see reflected from the feather.
When light hits the feather, the size of these holes determines how the light is scattered and thus the color that is reflected, the team says. Larger holes mean a broader wavelength reflectance of light, which creates the color white. A smaller, more compact hole results in the color blue.
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| Andrew J. Parnell, University of Sheffield |
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The variations in cavity size in the sponge-like keratin material of the feather determine the color we see reflected from it. |
Through these controlled changes, the team says, the jay can create the vivid feather colors—ranging from ultraviolet to blue to white—believed to aid the birds in recognizing one another.
The level of control is so refined that the jay is able to pattern these different colors along an individual feather barb—which would be the same as a single human hair having many different colors along its length. (The keratin material composing the feather is exactly the same as that found in human hair and nails.)
Pigments vs. Structural Color
According to the scientists, colors created by pigments would fade over time, but color created according to structural changes will remain intact.
This, they say, is why birds’ feathers don’t turn gray as a bird ages. Humans, however, depend on pigments for hair color; pigment production changes as we age, leading to our own gray hair.
According to the team’s lead author, Dr. Andrew Parnell of the university’s Department of Physics and Astronomy, understanding this link between color reflectance and the size and density of the holes in the spongy nanostructure means that long-lasting colored coatings and materials could be created synthetically.
“Current technology cannot make colour with this level of control and precision—we still use dyes and pigments,” he explained. “Now we’ve learnt how nature accomplishes it, we can start to develop new materials such as clothes or paints using these nanostructuring approaches.”
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| © iStock.com / llona5555 |
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The level of control of the nanostructure is so refined that the jay is able to pattern these different colors along an individual feather barb. |
He foresees a time when a red sweater created through this method would always retain its color and never fade in the wash.
These properties could also lead to long-term benefits in the paints and coatings industry.
Researcher Dr. Daragh McLoughlin, of AkzoNobel’s Decorative Paints Material Science Research Team, suggested that this method could lead to “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," he added.
About the University of Sheffield
The University of Sheffield, located in South Yorkshire, was voted number one university in the U.K. for Student Satisfaction by Times Higher Education in 2014. In the last decade it also has won four Queen’s Anniversary Prizes in recognition of the outstanding contribution to the U.K.’s intellectual, economic, cultural and social life.
It boasts five Nobel Prize winners among former staff and students, and its alumni, the school says, go on to hold positions of great responsibility and influence all over the world, making significant contributions in their chosen fields.
Global research partners and clients include Boeing, Rolls-Royce, Unilever, AstraZeneca, Glaxo SmithKline, Siemens and Airbus, as well as many U.K. and overseas government agencies and charitable foundations.
Tagged categories: Coating Materials; Colleges and Universities; Color retention; Colorants; Fade-Resistant Color; Research
