Space Industry and Business News  





.
TECH SPACE
Researchers Discover Optical Secrets of Metallic Beetles

Pictures of the Chrysina aurigans (left) and the Chrysina limbata (right) beetle specimens displaying their brilliant golden and silver appearance, respectively. Credit: Eduardo M. Libby.
by Staff Writers
Washington DC (SPX) Apr 27, 2011
Costa Rica was once regarded as the poorest of all the colonies of the Spanish Empire, sadly deficient in the silver and gold so coveted by conquistadors. As it turns out, all of the glittering gold and silver those explorers could have ever wanted was there all along, in the country's tropical rainforests-but in the form of two gloriously lustrous species of beetle.

Today, the brilliant gold- (Chrysina aurigans) and silver-colored (Chrysina limbata) beetles have given optics researchers new insights into the way biology can recreate the appearance of some of nature's most precious metals, which in turn may allow researchers to produce new materials based on the natural properties found in the beetles' coloring.

A team of researchers at the University of Costa Rica has found that the beetles' metallic appearance is created by the unique structural arrangements of many dozens of layers of exo-skeletal chitin in the elytron, a hardened forewing that protects the delicate hindwings that are folded underneath. A paper about the discovery appears in the first issue of the Optical Society's (OSA) newest open access journal, Optical Materials Express, which launched this month.

The beetles were captured in the University of Costa Rica's Alberto Brenes Mesen Biological Reserve, a tropical rainforest environment. "The metallic appearance of these beetles may allow them to be unnoticed, something that helps them against potential predators," says physicist and study leader William E. Vargas. The surface of their elytra "reflects light in a way that they look as bright spots seen from any direction," he explains.

"In a tropical rainforest, there are many drops of water suspended from the leaves of trees at ground level, along with wet leaves, and these drops and wet leaves redirect light by refraction and reflection respectively, in different directions. Thus, metallic beetles manage to blend with the environment."

To interpret the cause of this metallic look, Vargas and his team assumed that a sequence of layers of chitin appears through the cuticle, with successive layers having slightly different refractive indices.. In these beetles, the cuticle, which is just 10 millionths of a meter deep, has some 70 separate layers of chitin-a nitrogen-containing complex sugar that creates the hard outer skeletons of insects, crabs, shrimps, and lobsters. The chitin layers become progressively thinner with depth, forming a so-called "chirped" structure.

"Because the layers have different refractive indices," Vargas says, "light propagates through them at different speeds. The light is refracted through-and reflected by-each interface giving, in particular, phase differences in the emerging reflected rays. For several wavelengths in the visible range, there are many reflected rays whose phase differences allow for constructive interference. This leads to the metallic appearance of the beetles."

This is similar to the way in which a prism breaks white light into the colors of the rainbow by refraction, but in the case of these beetles, different wavelengths, or colors of light are reflected back more strongly by different layers of chitin. This creates the initial palette of colors that enable the beetles to produce their distinctive hues. The mystery the researchers still needed to understand in more detail, however, was how the beetles could so perfectly create the structure causing the brilliant metallic tones of silver and gold.

Using a device they specially designed to measure the reflection of light when it strikes the curved surface of the beetles' elytra, Vargas and his colleagues found that as light strikes the interface between each successive layer (the first interface being the boundary between the outside air and the top chitin layer), some of its energy is reflected and some is transmitted down to the next interface.

"This happens through the complete sequence of interfaces," Vargas says.

Because a portion of the light is reflected, it combines with light of the exact same wavelength as it passes back through layer upon layer of chitin, becoming brighter and more intense.

Ocean waves can exhibit the same behavior, combining to produce rare but powerful rogue waves. In the case of the beetles, this "perfect storm" of light amplification produces not only the same colors but also the striking sheen and glimmer that we normally associate with fine jewelry.

In the two beetle species, interference patterns are produced by slightly different wavelengths of light, thus producing either silver or gold colors.

"For the golden-like beetle, the constructive interference is found for wavelengths larger than 515 nm, the red part of the visible wavelength range," Vargas says, "while for the silver-like beetle it happens for wavelengths larger than 400 nm-that is, for the entire visible wavelength range."

"The detailed understanding of the mechanism used by the beetles to produce this metallic appearance opens the possibility to replicate the structure used to achieve it," Vargas says, "and thus produce materials that, for example, might look like gold or silver but are actually synthesized from organic media."

This potentially could lead to new products or consumer electronics that can perfectly mimic the appearance of precious metals. Other products could be developed for architectural applications that require coatings with a metallic appearance. Vargas notes that in the solar industry, for example, chirped multilayer reflectors could be used as back layers supporting the active or light-absorbing medium, to improve the absorption of the back-reflected light.

The article, "Visible light reflection spectra from cuticle layered materials," by Cristian Campos-Fernandez, Daniel E. Azofeifa, Marcela Hernandez-Jimenez, Adams Ruiz-Ruiz and William E. Vargas appears in the journal Optical Materials Express.




Share This Article With Planet Earth
del.icio.usdel.icio.us DiggDigg RedditReddit
YahooMyWebYahooMyWeb GoogleGoogle FacebookFacebook



Related Links
Optical Materials Express
Space Technology News - Applications and Research



Tempur-Pedic Mattress Comparison

Newsletters :: SpaceDaily Express :: SpaceWar Express :: TerraDaily Express :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News
TECH SPACE
Lightning-fast materials testing using ultrasound
Munich, Germany (SPX) Apr 25, 2011
For years, ultrasound has proven to be a valuable tool in non-destructive materials testing. However, the demands of modern production conditions are increasing all the time. Researchers at Fraunhofer have now developed a new, more reliable process that delivers testing results at a rate that is up to a hundredfold higher. Expectant mothers are familiar with the procedure: the physician ex ... read more

.
Get Our Free Newsletters Via Email
  


TECH SPACE
Lake life around Chernobyl said thriving

Researchers Discover Optical Secrets of Metallic Beetles

Sony challenges iPad in tablet war

A scratched coating heals itself

TECH SPACE
Lockheed Martin Demonstrates Integration of MONAX Communications System with Air Force Base Network

Preparations Underway As US Army Gears Up For Large-Scale Network Evaluations

Global Military Communications Market In 2010

Raytheon BBN Technologies To Protect Internet Comms For Military Abroad

TECH SPACE
Ariane Ariane 5 enjoys second successful launch for 2011

Ariane rocket launches two telecoms satellites

SpaceX aims to put man on Mars in 10-20 years

ULA Launches Fifth NRO Mission In Seven Months

TECH SPACE
GPS IIF Satellite Delivered to Cape Canaveral

S. Korea probes Apple about tracking feature

SecuraPets Introduces Better Way To Find Lost Pets

Topcon First Major Company To Track New GLONASS K1 Satellite Signals

TECH SPACE
Novel ash analysis validates volcano no-fly zones

Owls fly for cameras in flight study

GE likely to fight jet engine cancellation

China to build $1bn airport in Chad

TECH SPACE
Zeroing in on the Elusive Green LED

Conducting ferroelectrics may be key to new electronic memory

LED efficiency puzzle solved

Super-Small Transistor Created, Artificial Atom Powered By Single Electrons

TECH SPACE
Running ring around hurricanes predictions

Belgium probes Google's Street View

Goa Seeks ISRO Expertise For Mapping Mangroves, Sand Dunes

Satellites can give advance hurricane info

TECH SPACE
Toxic chemicals found in pet dogs

Toxic mud disaster leaves deep scars in Hungary

Britain issues first smog warning of the summer

Mercury On The Rise In Endangered Pacific Seabirds


The content herein, unless otherwise known to be public domain, are Copyright 1995-2010 - SpaceDaily. AFP and UPI Wire Stories are copyright Agence France-Presse and United Press International. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by SpaceDaily on any Web page published or hosted by SpaceDaily. Privacy Statement