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Friday, June 18, 2010

The secret of butterfly colors

Butterfly wing colors depend not on pigment within the wings but on the effect of light on microscopic structures on the wing surfaces. Although this has been understood for some time, it has been impossible to replicate the colors artificially. Mathias Kolle and his colleagues from the University of Cambridge have invented a way to manufacture the tiny color-producing structures.

Electron micrograph of natural butterfly wing: This scanning electron micrograph shows that the surface of a wing scale is covered with concavities.

Credit: Mathias Kolle, University of Cambridge

The team used the Indonesian Peacock or Swallowtail butterfly (Papilio blumei), shown above, as a model. This butterfly appears green to our naked eyes, but can become a brilliant blue under other optical conditions. The intense colors are a direct result of intricate microscopic structures. The researchers were able to successfully manufacture those vibrant colors by using nanofabrication processes, such as atomic layer deposition.

Electron micrograph of artificial structure: This SEM image of concavities is covered by a conformal multilayer stack of 11 alternating layers of titania and alumina.

Credit: Mathias Kolle, University of Cambridge

The scientists anticipate a number of uses for their new color manufacturing process, including creating optical signatures for documents and bank notes.