While a large number of colours in nature are produced by pigments some, like the vibrant feathers of many types of birds, are instead produced by nanostructures.

An interdisciplinary team at Yale University has found that these structures, which appear sponge-like with air bubbles, form by a process of self-assembly. They compared the natural nanostructures to examples of materials undergoing phase separation in which mixtures of different materials become unstable and separate from one another. In the case of feathers, bubbles of water form in a protein-rich soup inside the living cells and are replaced by air as the feather grows forming ?-keratin and air nanostructures. The colour produced depends on the exact size and shape of the individual nanostructure.

The research provides important insights into how organisms use self-assembly of materials at the nanoscale to produce colour. The researchers are also interested in the potential technological applications of their finding to produce novel optical materials.

Publication: Soft Matter

Source: Nanowerk