Issue Date: June 21, 2010
The Butterfly Effect
A new examination of butterflies’ brightly colored wing scales has the photonics community all aflutter. For the first time, researchers have used small-angle X-ray scattering (SAXS) on single butterfly scales to characterize the three-dimensional photonic nanostructures that make butterfly wings so luminous (Proc. Natl. Acad. Sci. USA, DOI: 10.1073/pnas.0909616107).
Yale University’s Richard O. Prum and coworkers looked at five different species from two butterfly families and found that the wing scales’ nanostructure is a single network of gyroid photonic crystals made of air and chitin—the same stuff that makes up the exoskeletons of crustaceans and other insects.
Other scientists had previously predicted that the scales have a gyroid structure, but they studied the scales with transmission electron microscopy, which tends to shrink samples, altering their nanostructures. Prum’s team turned to SAXS, a technique that’s only recently been used to study natural photonics materials.
“To resolve structures this large,” Prum says of the butterfly wing scales, “you need to look at scattered waves that are at very small angles to, and therefore very close to, the incident beam. Until recently, this capability was not available,” he explains.
Prum’s team also postulates a mechanism for gyroid formation based on the self-organizing physical dynamics of biological lipid-bilayer membranes. By mimicking the process, it might be possible to engineer superior photonic crystals, they say.
"Once again, advancements in nanocharacterization technologies have brought exciting new knowledge of materials on the nanoscale," comments Radislav A. Potyrailo, a principal scientist with GE Global Research, in Niskayuna, N.Y., who has studied the photonic properties of butterfly wings. "One of the significant aspects of this work is that it provides new insights on the formation of these photonic structures in nature. This new knowledge promises to propel the technologies focused on nanofabrication of 3-D nanostructures."
- Chemical & Engineering News
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