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When you see a butterfly flutter in your garden have you noticed how its wing colours seem to be iridescent? They shine, shimmer and even look like they are changing colours from blue to green to yellow.
This extravagant quality of butterfly wings is so powerful that even an airplane flying above the Amazon Rainforest canopy could easily detect the movement of the blue butterflies miles from above.
So what is it that butterflies possess that makes their wings shimmer and shine? The colour of butterfly wings is due to two factors. One is the presence of pigments, like most other living things. Plants have chlorophyll which reflects green while absorbing all other colours of the light spectrum. That is why they appear green. In the same way, butterflies have certain pigments like the melanin that makes their wing appear brown or black.
Additionally, and this is the most interesting part, butterfly wings are actually made up of thousands of scales that form a geometric pattern that acts as a crystal of sorts. So, light passing through the scales is reflected a number of times and at different angles creating the amazing colour and the stunning iridescence.
Also read: Tiny National Park shows Huge Butterfly Biodiversity
The colour is not due to a chemical pigment that might fade. It is pure physics with the application of refraction, and reflection of light. That is why this kind of colour is brighter, consistent and produces such marvelous spectacle when the wings flap.
In 2010, a researcher Vinodkumar Saranathan from Yale University used an X-ray scattering technique to generate 3-D images of the butterfly wings of the lycaenid & papilionid families.
He found that the complex structure of the wings were tiny structures called gyroids that diffract sunlight like a crystal. The size of the gyroid determines the colour. If you could shrink the structure it would become bluer. If you could expand it, it would be redder.
Butterflies have been doing this for millions of years and now scientists are trying to replicate the same technique to produce materials that remain true to their colours.
