Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Scientists Unlock Optical Secrets of Jewel Beetles

27.07.2009
A small green beetle may have some interesting lessons to teach scientists about optics and liquid crystals – complex mechanisms the insect uses to create a shell so strikingly beautiful that for centuries it was used in jewelry.

In an article to be published in the July 24 issue of the journal Science, researchers provide a detailed analysis of how a jewel beetle (Chrysina gloriosa) creates the striking colors using a unique helical structure that reflects light of two specific colors – and of only one polarization: left circular polarization.

The reflecting structures used by the beetle consist predominately of three different polygonal shapes whose percentages vary with the curvature of the insect’s shell.

“Iridescent beetles, butterflies, certain sea organisms and many birds derive their unique colors from the interaction of light with physical structures on their external surfaces,” said Mohan Srinivasarao, a professor in the School of Polymer, Textile and Fiber Engineering at the Georgia Institute of Technology. “Understanding how these structures give rise to the stunning colors we see in nature could benefit the quest for miniature optical devices and photonics.”

With support from the National Science Foundation, Srinivasarao and colleagues Vivek Sharma, Matija Crne and Jung Ok Park used two different microscopy techniques to study the surface structures on the shell of the beetle. What they found confirmed earlier suggestions that the colors are produced from liquid crystalline material, which self-assembles into a complex arrangement of polygonal shapes each less than 10 microns in size.

“When we looked at the beetle’s surface, we found tiles in the shapes mostly of hexagons, pentagons and heptagons,” Srinivasarao said. “These patterns arise, we think, because of the nature of the cholesteric liquid crystal and how the liquid crystal phase structures itself at the interface between air and fluid. We think these patterns result because the liquid crystal must have defects on the surface when exposed to air, and those defects create the patterns in the beetle’s shell or exoskeleton.”

Because of simple geometric restrictions, the percentage of each shape depends on the curvature of that particular section of the shell. “This is really a pattern formation issue,” said Srinivasarao. “It is difficult to pack only hexagons onto a curved surface. On flat surfaces, there are fewer defects in the form of five- and seven-sided cells.”

In addition, the five- and seven-sided cells normally appear in pairs, an issue also dictated by the geometric difficulties of packing the shapes onto curved surfaces. The researchers found very similar structures in the ten different beetles purchased from an insect supply house.

Liquid crystalline materials are valuable industrially, used in displays for laptop computers, portable music players and other devices. They are also used in children’s thermometers, where temperature affects the color of light reflected from the material, indicating whether or not a child has a fever.

While the structures are determined genetically, their final form depends on the living conditions the beetle experiences during its growth and development, Srinivasarao noted.

The fact that these jewel beetles reflect circular polarization was identified in the early 1900s by a Nobel Prize-winning physicist, A.A. Michelson, who hypothesized that the circular polarization might result from a “screw structure” within the insect’s cuticle, but he did not elaborate on it further. The solidified structures produced from a cholesteric liquid crystal and its defects on the beetle’s shell reflect bright green light with a wavelength of 530 nanometers mixed with yellow light in a wavelength of 580 nanometers.

“The most dramatic way to get saturated color is through what this beetle does with the circularly-polarized light,” Srinivasarao said. “The reflection is very metallic and angle-dependent, and this is due to the helical pitch of the cholesteric liquid crystal.”

Sunlight normally contains light in equal quantities with a left circular polarization and a right circular polarization. The jewel beetle’s exoskeleton, however, reflects only light with a left circular polarization.

How the beetles benefit from the specific color and polarization isn’t known for sure, but scientists speculate that the optical properties may confuse predators, causing them to misjudge the location of the insects – or suggest that they may not be good to eat. The colors may also help the insects find mates.

In future research, Srinivasarao hopes to study other insects that use complex structures to create unique colors. He believes that scientists still have a lot to learn by studying the optical structures of beetles and other insects.

“We are just now starting to catch up with what these beetles have been doing for many, many years,” he said. “There are hundreds of thousand of species, and the way they generate color is just stunning – especially since it is all done with water-based systems, mostly based on the biopolymer chitin. This is self-assembly at several levels, and we need to learn a lot more to duplicate what these insects do.”

Technical Contact: Mohan Srinivasarao (404-894-9348); E-mail: (mohan.srinivasarao@ptfe.gatech.edu).

John Toon | Newswise Science News
Further information:
http://www.gatech.edu

More articles from Physics and Astronomy:

nachricht A two-atom quantum duet
12.11.2018 | Institute for Basic Science

nachricht Improving understanding of how the Solar System is formed
12.11.2018 | Goethe-Universität Frankfurt am Main

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A Leap Into Quantum Technology

Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.

In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...

Im Focus: Research icebreaker Polarstern begins the Antarctic season

What does it look like below the ice shelf of the calved massive iceberg A68?

On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.

Im Focus: Penn engineers develop ultrathin, ultralight 'nanocardboard'

When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure

Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...

Im Focus: Coping with errors in the quantum age

Physicists at ETH Zurich demonstrate how errors that occur during the manipulation of quantum system can be monitored and corrected on the fly

The field of quantum computation has seen tremendous progress in recent years. Bit by bit, quantum devices start to challenge conventional computers, at least...

Im Focus: Nanorobots propel through the eye

Scientists developed specially coated nanometer-sized vehicles that can be actively moved through dense tissue like the vitreous of the eye. So far, the transport of nano-vehicles has only been demonstrated in model systems or biological fluids, but not in real tissue. The work was published in the journal Science Advances and constitutes one step further towards nanorobots becoming minimally-invasive tools for precisely delivering medicine to where it is needed.

Researchers of the “Micro, Nano and Molecular Systems” Lab at the Max Planck Institute for Intelligent Systems in Stuttgart, together with an international...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

“3rd Conference on Laser Polishing – LaP 2018” Attracts International Experts and Users

09.11.2018 | Event News

On the brain’s ability to find the right direction

06.11.2018 | Event News

European Space Talks: Weltraumschrott – eine Gefahr für die Gesellschaft?

23.10.2018 | Event News

 
Latest News

In focus: Peptides, the “little brothers and sisters” of proteins

12.11.2018 | Life Sciences

Materials scientist creates fabric alternative to batteries for wearable devices

12.11.2018 | Materials Sciences

A two-atom quantum duet

12.11.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>