Scientists studying tropical butterflies have created replica models of their wings using technology that could be used to combat fraudsters.
Brightly coloured patterns on beetles, butterflies and other insects could now be reproduced on bank notes and passports to minimise the risk of forgery.
Mimicking these iridescent patterns has long eluded scientists as they are produced by light bouncing off microscopic structures in the insects’ wings.
But after studying the Indonesian Peacock Swallowtail butterfly, experts at the University of Cambridge have made realistic imitation copies of the butterfly’s wings.
The distinctive Papilio blumei is found only on the island of Sulawesi in Indonesia and has a wingspan of three to three-and-a-half inches.
The wings of the Swallowtail have an intricate, microscopic make up resembling the structure of an egg carton.
It is due to their shape and the alternate layers of air and cuticle within the wings that they produce such depth and intensity of colour.
But Mathias Kolle, working with Professor Ullrich Steiner and Professor Jeremy Baumberg, found a way to produce structurally identical replicas of butterfly scales.
The strikingly coloured copies are created in the lab from a combination of nanofabrication procedures including self-assembly and atomic layer deposition.
Now Mathias Kolle and his colleagues are hoping to use their research in the pursuit of applications in security printing to foil counterfeiters.
He said: ”We have unlocked one of nature’s secrets and combined this knowledge with state-of-the-art nanofabrication to mimic the intricate optical designs found in nature.
”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.
”These artificial structures could be used to encrypt information in optical signatures on banknotes or other valuable 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.”
The team’s research has demonstrated that the colours of the butterfly may act as a subtle form of protection, allowing it to appear one colour to mates and another to foes.
Kolle said: ”The shiny green patches on this tropical butterfly’s wing scales are a stunning example of nature’s ingenuity in optical design.
”Seen with the right optical equipment these patches appear bright blue, but with the naked eye they appear green.
”This could explain why the butterfly has evolved this way of producing colour.
”If its eyes see fellow butterflies as bright blue, while predators only see green patches in a green tropical environment, then it can hide from predators at the same time as remaining visible to members of its own species.”
The research was funded by the Engineering and Physical Sciences Research Council and the Cambridge Newton Trust.
The study entitled ”Mimicking the colourful wing scale structure of the Papilio blumei butterfly” is published in Nature Nanotechnology journal on 30 May.
