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New butterfly-wing technology could foil counterfeiters

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June 1, 2010

The bright green wings of the P. blumei butterfly result from the mixing of the different ...

The bright green wings of the P. blumei butterfly result from the mixing of the different colors of light that are reflected from different regions of the scales (Image: Mathias Kolle, University of Cambridge)

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Counterfeiting is a crime as old as money itself. It causes a reduction in the value of real money and can add to company losses, as they are not reimbursed for counterfeits. In 1996 Australia became the first country to have a full series of circulating polymer banknotes, which are difficult to counterfeit because they cannot be successfully reproduced by photocopying or scanning. Now scientists have discovered a way of mimicking the stunningly bright and beautiful colors found on the wings of tropical butterflies, that could help make banknotes and credit cards even harder to forge.

The striking iridescent colors displayed on beetles, butterflies and other insects have long fascinated both physicists and biologists, but mimicking nature's most colorful, eye-catching surfaces has proved elusive. This is partly because rather than relying on pigments, these colors are produced by light bouncing off microscopic structures on the insects' wings.

Mathias Kolle, working with Professor Ullrich Steiner and Professor Jeremy Baumberg of the University of Cambridge, studied the Indonesian Peacock or Swallowtail butterfly (Papilio blumei), whose wing scales are composed of intricate, microscopic structures that resemble the inside of an egg carton. Because of their shape and the fact that they are made up of alternate layers of cuticle and air, these structures produce intense colors.

Using a combination of nanofabrication procedures – including self-assembly and atomic layer deposition – Kolle and his colleagues made structurally identical copies of the butterfly scales, and these copies produced the same vivid colors as the butterflies' wings.

As well as helping scientists gain a deeper understanding of the physics behind these butterflies' colors, being able to mimic them has promising applications in security printing.

"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," he says.

Unlocking the nanostructure of butterfly wings also holds promise in other areas. As we reported last year, researchers hope to develop various optically-active structures, such as optical diffusers or coverings that maximize solar cell absorption by replicating the biotemplate of butterfly wings.

Intriguingly, the butterfly may also be using its colors to encrypt itself – appearing one color to potential mates but another color to predators.

Kolle explains, "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 color. 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 results of the team’s research appear in the journal Nature Nanotechnology.

About the Author
Darren Quick Darren's love of technology started in primary school with a Nintendo Game & Watch Donkey Kong (still functioning) and a Commodore VIC 20 computer (not still functioning). In high school he upgraded to a 286 PC, and he's been following Moore's law ever since. This love of technology continued through a number of university courses and crappy jobs until 2008, when his interests found a home at Gizmag.   All articles by Darren Quick
2 Comments

New Zealand also went to polymer bank notes in 1999. And we don't have any currency less than 10 cents. When I go to North America, my wallet is packed full of pennies in a matter of hours and they're worth as close to zero as you can imagine. Something to consider.

warren52nz
2nd June, 2010 @ 02:51 pm PDT

Very good invention to foil counterfeit.

Dr.A.Jagadeesh Nellore(AP),India

Anumakonda Jagadeesh
11th June, 2010 @ 04:18 pm PDT
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