Dr. Nimmy John V
Sep 28,2020
1:37pm
“ Why am I so brilliantly coloured?”, asks a BUTTERFLY
All of us enjoy watching butterflies. They can take us to a calm and peaceful mindset. Why is it so? Because, its brilliantly coloured wings give us that serene feelings. Have you ever wondered how they got these eye-catching colours?
There are many factors that contribute to the colour of the butterfly. That includes pigments, light absorption and, most importantly, the nanostructures on the wings of butterflies. Have you heard about nanostructures? It is just simple. Structures in nanometer size are termed nanosized structures. A nanometer is as small as 10-9 meter. To understand what is nano size, you just look at a strand of your hair. You may know that the diameter of a human hair is 80,000 - 100,000 nm. I think now you can relate the size. When we take a closer look at the wings of butterflies through an electron microscope (microscope is used to view particles up to 1nm in size) we can find layers of nanostructured scales on it, which can absorb light in the visible region of the light spectrum (VIBGYOR). Colours are produced when the light waves interact with these nanostructured scales on the wings of butterflies. When light falls on the layers of nanostructured scales, it gets reflected and the reflection from different layers can undergo interference and can produce bright colours. These nanostructures have a selection technique which reflects only certain wavelengths. Shape, thickness and size of nanostructured scales contribute to the colour selection. The angle of reflection, frequency of light and the spacing of the layers will also contribute to it. That is the reason why our eyes can see different coloured butterflies. The interaction of light on surfaces with periodic nanoscale structures are responsible for the brightest and vibrant colours in nature.
Scientists inspired by the light diffraction technique tried to mimic the 3D nanostructure of butterfly wings. They created a nano-sized array of holes to produce a butterfly effect. The application of the above butterfly effect was to fight counterfeiting currency. When light falls on these nano arrays of holes, the interference of light creates a unique image. These 3D nanostructures have application in the area of Photonic crystals, beam splitters etc.