Inspired by the bright colours of a bird's feathers, a Japanese team has worked out how to create structural colours that don't change colour depending on the angle you view them.
The team from Nagoya University have worked out how to reproduce the colour of Steller's jay, a North American bird with a deep blue plumage.
"The Steller's jay's feathers provide an excellent example of angle-independent structural colour," said Yukikazu Takeoka, an Associate Professor in the Department of Molecular Design & Engineering at Nagoya.
"This colour is enhanced by dark materials, which in this case can be attributed to black melanin particles in the feathers."
In most cases, structural colours appear to change when viewed from different perspectives. For example, imagine the way that the colours on the underside of a CD appear to shift when the disc is viewed from a different angle.
The difference in Steller's jay's blue is that the structures, which interfere with light, sit on top of black particles that can absorb a part of this light. This means that at all angles, however you look at it, the colour of the Steller's Jay does not change.
The team used a "layer-by-layer" approach to build up films of fine particles that recreated the microscopic sponge-like texture and black backing particles of the bird's feathers.
To mimic the feathers, the researchers covered microscopic black core particles with layers of even smaller transparent particles, to make raspberry-like particles. The size of the core and the thickness of the layers controlled the colour and saturation of the resulting pigments. Importantly, the colour of these particles did not change with viewing angle.
"Our work represents a much more efficient way to design artificially produced angle-independent structural colours," said Takeoka.
"We still have much to learn from biological systems, but if we can understand and successfully apply these phenomena, a whole range of new metamaterials will be accessible for all kinds of advanced applications where interactions with light are important."
He says artificially harnessing this effect could allow us to engineer new materials for applications such as solar cells and chameleon-like adaptive camouflage.
[Steller's jay. Photo: Pixabay]
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