UK: Science imitates nature's bright colours

Scientists have found a way to create tiny structures that reflect light in such a way they produce bright colours. They copied structures found on insects, such as butterflies and beetles, and say their discovery could eventually be used by the printing industry.

The researchers at the University of Cambridge studied the Indonesian Peacock or Swallowtail butterfly (Papilio blumei). Its wing scales are composed of intricate, microscopic structures that look like the inside of an egg carton.

It is those structures, rather than pigment, that produce the bright colours on the butterfly's wings. The scientists say it is their shape and the fact they consist of alternating layers of cuticle and air that produce such intense colours in the butterfly and other brightly coloured insects.

Mathias Kolle, working with Professor Ullrich Steiner and Professor Jeremy Baumberg, made structurally identical copies of the butterfly scales, and the copies produced the same vivid colours as the butterfly's wings.

"We have unlocked one of nature's secrets and combined this knowledge with state-of-the-art nano-fabrication to mimic the intricate optical designs found in nature," said Kolle.

"Although nature is better at self-assembly than we are, we have the advantage that we can use a wider variety of artificial, custom-made materials to optimise our optical structures."

Kolle said such artificial structures could be used to encrypt information in optical signatures on banknotes or other items to protect them against forgery.

"We still need to refine our system but in future we could see structures based on butterflies' wings shining from a £10 note or even our passports," he said.

Kolle said butterflies already appeared to be using the colour-producing structures for a form of encryption.

Their wings would appear to be different colours depending on the optical equipment used to view them. So their wings would appear to be one colour to potential mates but another colour to predators.

"Seen with the right optical equipment these patches appear bright blue, but with the naked eye they appear green," Kolle said.

The research is published in Nature Nanotechnology.