Biomimetic Butterfly Coating Could Save Lives

http://fc02.deviantart.net/fs14/i/2007/067/2/5/Blue_Morpho_Butterfly_Wings_by_Enchantedgal_Stock.jpg

Blast-induced traumatic brain injury (TBI) is the "signature wound" of the recent conflicts Iraq and Afghanistan. Without any real quantitative method to indicate the magnitude of blast exposure, soldiers affected may not receive appropriate medical care. Researchers at the University of Pennsylvania School of Medicine have recently developed at new blast badge inspired by the wings of butterflies.

You may have noticed that many butterfly's wings are extraordinarily vibrant in color. How do these insects manage to create colors from the most iridescent of blues and greens to near pitch-black? The answer lies in the hierarchical surface nanostructure of the wings themselves. A butterfly's wing is covered in thousands of microscopic scales, which are in turn covered with very small ridges called cuticles. Each cuticle is further made up of several horizontal ridges. When a cuticle is cross sectioned, it loosely resembles a fir tree. This type of coloration is known as structural coloration.

http://static.ddmcdn.com/gif/butterfly-color-wing.jpg

This very fine structure is what gives the insects their brilliant colors.  As light hits these ridges on the wings, some wavelengths are absorbed and others are reflected back. This is what produces the pure vibrant colors many butterflies are known for. Also, as light is reflected off of the wing's surface, each ridge sends the light to a viewers eyes slightly out of phase with each other. This causes the iridescent effect where color changes slightly with viewing angle and gives a somewhat rainbow effect.

How does this help with determining blast exposure though? The researchers at the University of Pennsylvania School of Medicine have created a patch which functions similarly to the cuticles on the wings of butterflies. Using holographic lithography (the application of light, usually UV, to a photosensitive material in order to fabricate small features), the team created "Layers of Swiss cheese with columns in between." The material is stable in the presence of temperature change and physical impact

http://images.gizmag.com/hero/blastbadge.jpg

 When undamaged they reflect a certain color, but when introduced to the shockwave of a blast, the columns collapse and the pores grow larger. This changes the wavelength of light that is reflected thus changing the color we perceive. The team or researchers has also designed the badges to deform according to different ranges of blast magnitudes. The badges could be made as small as the fill-in-the-blank circles used on multiple choice tests and sewn onto soldiers clothing. This invention could be used to accurately diagnose soldiers for TBI's, whereas other methods are unreliable, and allow for appropriate and timely medical attention.