Structural color

The brilliant iridescent colours of the male Peacock's tail feathers are created by structural coloration, as first noted by Isaac Newton and Robert Hooke.

Structural coloration is a coloring that results from the special structure of the surface. Sometimes structural coloration is combined with pigments: for example, peacock tail feathers are pigmented brown, but their structure makes them appear blue, turquoise, and green, and often they appear iridescent.

English scientists Robert Hooke and Isaac Newton were the first who observed structural coloration. Thomas Young described its principle a century later and called it wave interference. Young described iridescence as the result of interference between reflections from several surfaces of thin films, combined with refraction as light enters and leaves such films. The geometry then determines that at certain angles, the light reflected from both surfaces adds (interferes constructively), while at other angles, the light subtracts. As a result, different colors appear at different angles.

Structural Color Media

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  Robert Hooke's 1665 Micrographia contains the first observations of structural colours.

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  In 1892, Frank Evers Beddard noted that Chrysospalax golden moles' thick fur was structurally coloured.

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  When light falls on a thin film, the waves reflected from the upper and lower surfaces travel different distances depending on the angle, so they interfere.

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  Electron micrograph of a fractured surface of nacre showing multiple thin layers

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  Butterfly wing at different magnifications reveals microstructured chitin acting as a diffraction grating

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  Drawing of 'firtree' micro-structures in Morpho butterfly wing scale

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  Structural coloration through selective mirrors in the emerald swallowtail

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  Magnificent non-iridescent colours of blue-and-yellow macaw created by random nanochannels