Colour me amazed!

Tapajyoti Das Gupta was winding up his work as a post-doctoral researcher at the Swiss Federal Institute of Technology in Lausanne in 2019 when a chance encounter set things off. Over the last few days, while working with the Scanning Electron Microscope (SEM), he met an artist who had booked a timeslot on the SEM to examine the internal structure of bird feathers, butterfly wings and some plants. Several birds, butterflies and plants owe their striking colours to their physical structure, not pigments. These structures are too small to be seen with the naked eye. But under the microscope, especially one as powerful as an SEM, the structures become visible. Because of their small size, they are called microstructures or nanostructures. When light falls on such materials, it is reflected and refracted in unique ways resulting in vivid colours. The colour produced depends on the size, shape and arrangement of the nanostructures and on the angle of the incident light.