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Eyes are anti-reflective: elephant hawk-moth

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Elephant hawk-moth / Nigel Jones / LicenseCC-by-nc-nd - Attribution Non-commercial No Derivatives

Eyes of nocturnal moths are anti-reflective due to nanoscale protrusions.

BIOMIMICRY TAXONOMY
Summary
Moths have unique sub-wavelength structures coating their eyes which dramatically minimize light reflection over a much broader range of wavelengths than conventional anti-reflective coatings. The outer surfaces of moth corneal lenses are covered with a regular pattern of conical protuberances, generally 200-300 nm in height and spacing. These protuberances reduce light reflection by creating a refractive index gradient between the air-lens interface, more gradually transitioning the change in light speed between the air and eye and hence minimizing reflection. These unique structures help moths evade detection by predators in moonlight and maximize light capture for seeing in the dark. Moth-eye inspired antireflective coatings that demonstrate high-performance over large band widths at low fabrication cost have recently been developed for solar panels, with many other potential products applications.
Excerpt
"Most moth eyes are made up of hexagonal sectors, each of which is filled with thousands of rows of nipple-like protrusions measuring only 300 nanometers. The value of this structure to the moth is that it interferes with transmission and reflection of light, which may protect it from predators as it forages in the moonlight." (Courtesy of the Biomimicry Guild)

"The eyes of moths have two characteristic optical structures that probably function to increase the light sensitivity: the tapetal mirror and the corneal nipple array (Miller, 1979). The tapetum is composed of tracheoles at the proximal portion of the rhabdom and reflects unabsorbed light back into the rhabdom, thus providing a second chance for light to be absorbed. The corneal nipple array, known as the ‘moth-eye’ structure, is a set of protuberances of height about 200•nm, acting as a thin-film antireflection coating. These structures are basically retained in the apposition eyes of true butterflies, but all species in the family Papilionidae lack both (Bernhard et al., 1970; Stavenga et al., 2006).” (Takemura et al. 2007)
About the inspiring organism
Med_elephant_hawk_moth.mittlerer_weinschwaermer_2 Elephant hawk-moth
Deilephila elpenor Linnaeus

Habitat(s): Shrubland
Learn more at EOL.org
Some organism data provided by: LepIndex: The Global Lepidoptera Names Index
Organism/taxonomy data provided by:
Species 2000 & ITIS Catalogue of Life: 2008 Annual Checklist

IUCN Red List Status: Unknown

Bioinspired products and application ideas

Application Ideas: Anti-reflective, anti-glare, self-cleaning coatings for solar cell collectors, windows, computer screens, flat-panel displays, vehicle dashboards, and optical elements. Super-hydrophobic coatings to prevent contamination, erosion, and bacterial accumulation. Improve the conversion efficiencies of crystalline silicon solar cells by mimicking moth eyes.

Industrial Sector(s) interested in this strategy: Manufacturing, energy, transportation, computing, coating, building, optics, photonics



Experts
Neurobiophysics
Doekele G. Stavenga
University of Groningen
The Jiang Group
Peng Jiang
Department of Chemical Engineering, University of Florida
References
Takemura, S-Y.; Stavenga, D.G.; Arikawa, K. 2007. Absence of eye shine and tapetum in the heterogeneous eye of Anthocharis butterflies (Pieridae). The Journal of Experimental Biology. 210: 3075-3081.
Learn More at Google Scholar Google Scholar  

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admin
over 5 years ago
This strategy is now being applied to solar cells as well:

http://physicsworld.com/cws/article/news/37711
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