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On A Limb / December 2005
Fly by Night
Hi-tech lighting has been the fly-tech lighting of butterflies for millions of years. Scientists have discovered that fluorescent patches on the wings of African swallowtail butterflies work in a very similar way to high emission light emitting diodes known as LED’s.
These high emission LEDs are an efficient variation on the diodes used in electronic equipment and displays. In 2001, researchers at the Massachusetts Institute of Technology (MIT) demonstrated a method for building a more efficient LED. Most light emitted from standard LEDs cannot escape, resulting in what scientists call a low extraction efficiency of light.
The LED developed at MIT used a two-dimensional photonic crystal to enhance the extraction of light and special reflectors to control the emission direction.
These high emission devices potentially offer a huge step up in performance over standard types. British scientists have now shown that African swallowtail butterflies evolved an identical method for signaling to each other in the wild. Wing scales on the swallowtails act as two dimensional photonic crystals, infused with pigment and structured in such a way that they produce intense fluorescence. Most of this light would be lost were it not for the pigment being located in a region of the wing which has evenly spaced micro-holes through it.
This slab of hollow air cylinders in the wing scales is essentially mother nature’s version of a 2D photonic crystal.
Like its counterpart in a high emission LED, the butterfly’s version prevents the fluorescent color from being trapped inside the structure and from being emitted sideways. The scales also have a type of mirror underneath them to upwardly reflect all the fluorescent light emitted down towards it, very similar to the special reflectors in high emission LED’s. The way light is extracted from the butterfly’s system is more than an analogy–it’s all but identical in design to the LED. Butterflies have been illuminating their world for eons. Human being are just now seeing the light.
Copyright © 2005-2006 A Woman's View. All rights reserved.
Femme Fair 2006
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