A team of physicists that visualized the internal nanostructure of an intact butterfly wing has discovered two physical attributes that make those structures so bright and colorful. Credit: © boule1301 / Fotolia
A team of physicists that visualized the internal nanostructure of an intact butterfly wing has discovered 2 physical attributes that make those structures so bright and colorful. “Over millions of years, butterflies have evolved sophisticated cellular mechanisms to grow brightly colored structures, normally for the purpose of camouflage as well as mating,” says A/prof Oleg Shpyrko, Physics, UC SD. “It’s been known for a century that the wings of these beautiful creatures contain what are called photonic crystals, which can reflect light of only a particular color.”
But exactly how these complex optical structures are assembled in a way that make them so bright and colorful remained a mystery. Shpyrko and Andrej Singer went to the Advanced Photon Source at the Argonne National Laboratory in Illinois, which produces coherent xrays very much like an optical laser By combining these laser-like xrays with an advanced imaging technique called “ptychography,” the physicists, in collaboration with physicists at Yale University and the Argonne National Laboratory, developed a new microscopy method to visualize the internal nanostructure of the tiny “scales” that make up the butterfly wing without cutting.
Scales from the wings of the Emperor of India butterfly consist of “highly oriented” photonic crystals. Photos by Andrej Singer, UC San Diego
Their examination of the scales of the Emperor of India butterfly, Teinopalpus imperialis, revealed that these tiny wing structures consist of “highly oriented” photonic crystals. “This explains why the scales appear to have a single color,” says Singer. “We also found through careful study of the high-resolution micrographs tiny crystal irregularities that may enhance light-scattering properties, making the butterfly wings appear brighter.”
These crystal dislocations or defects occur when an otherwise perfectly periodic crystal lattice slips by one row of atoms. “Defects may have a negative connotation, but they are actually very useful in improving materials,” explains Singer. “For example, blacksmiths have learned over centuries how to purposefully induce defects into metals to make them stronger. ‘Defect engineering’ is also a focus for many research teams and companies working in the semiconductor field. In photonic crystals, defects can enhance light-scattering properties through an effect called light localization.”
“In the evolution of butterfly wings,” he adds, “it appears nature learned how to engineer these defects on purpose.” http://ucsdnews.ucsd.edu/pressrelease/x_ray_snapshot_of_butterfly_wings_reveals_underlying_physics_of_color
Recent Comments