The black color of butterfly wings is not just a black material, but a complex structure for absorbing light that can be compared to Vantablack, a nanotube material with record low incident light reflectance. This conclusion was reached by researchers from Duke University (USA), who were able to measure the parameters of the scales on the wings of these insects. They are much more complex than an array of nanotubes, but inexplicably thinner by several times.
If the official absorption coefficient of incident light for Vantablack is 99.96%, then for scales on the wings of a butterfly it is only two hundredths of a percent lower - 99.94%. Visually, both look like absolute blackness, a hole in space. But if Vantablack was created by people, then butterfly wings are the result of evolution. However, scientists still have no idea why they need such a radically black color.
With a thickness of only 3-4 nanometers (20% of the thickness of the synthetic material Vantablack), the scales of the wings were very complex. There are ridges, ridges, cells, honeycomb-like areas, sponge-like, etc. It was found that the darkest areas fall on fragments either with a ribbed surface or with thick legs at the base of the honeycomb. The same areas that do not have such relief elements reflect 16 times more light. Therefore, they are dark brown rather than black.
In general, the unprecedented level of light absorption in this biostructure is achieved due to the surface roughness and the huge absorption area. But how does the nanostructure inside the flake withstand this load, being many times thinner and more fragile than carbon nanotubes? In addition, given the number of butterflies with black wings in the world, there is a chance that reproducing such a structure will be easier and cheaper than creating new variations of Vantablack. And then the world will open up the broadest possibilities for its application.