Study reveals unique physical, chemical properties of cicada wings

April 14, 2020

CHAMPAIGN, Ill. -- Biological structures sometimes have unique features that engineers would like to copy. For example, many types of insect wings shed water, kill microbes, reflect light in unusual ways and are self-cleaning. While researchers have dissected the physical characteristics that likely contribute to such traits, a new study reveals that the chemical compounds that coat cicada wings also contribute to their ability to repel water and kill microbes.

The scientists report their findings in the journal Advanced Materials Interfaces.

The researchers looked at the physical traits and chemical characteristics of the wings of two cicada species, Neotibicen pruinosus and Magicicada casinnii. N. pruinosus is an annual cicada; M. casinnii emerges from the soil once every 17 years. Previous studies have shown that both species have a highly ordered pattern of tiny pillars, called nanopillars, on their wings. The nanopillars contribute to the wings' hydrophobicity - they shed water better than a raincoat - and likely play a role in killing microbes that try to attach to the wings.

"We knew a lot about the surface structure of cicada wings before this study, but we knew very little about the chemistry of those structures," said
To study nanopillar chemistry, Román-Kustas developed a method to gradually extract the compounds on the surface without damaging the overall structure of the wings. She placed each wing in solvent in an enclosed chamber and slowly microwaved each one.

"We extracted all these different compounds over different time periods, and then we analyzed what came off," Román-Kustas said. "And we also looked at the corresponding changes in the nanopillar structure."

The effort revealed that cicada wings are coated in a stew of hydrocarbons, fatty acids and oxygen-containing molecules like sterols, alcohols and esters. The oxygen-containing molecules were most abundant deeper in the nanopillars, while hydrocarbons and fatty acids made up more of the outermost nanopillar layers.

"Finding these particular molecules on the surface is not a surprise," Alleyne said. "Hydrocarbons and fatty acids on insect cuticle is fairly common."

The ratio of surface chemicals differed between the two cicada species, as did their nanopillar structures.

The study revealed that altering the surface chemicals also changed the nanopillar structure. In the N. pruinosis cicadas, the nanopillars began to shift in relation to one another as the chemicals were extracted, and later shifted back to a more parallel configuration. This also changed the wings' wettability and anti-microbial characteristics.

The wings of the M. cassinni cicadas had shorter nanopillars and a higher proportion of hydrophobic compounds on their surface. Their nanopillar configuration orientation did not change as a result of extracting their surface chemicals.

While preliminary, the new findings offer insight into the interplay of structure and chemistry in determining function, Alleyne said. By dissecting these characteristics, the researchers hope to one day design artificial structures with some of the same surface traits. Finding materials that shed water and kill microbes, for example, would be useful in many applications, from agriculture to medicine, she said.
-end-
Alleyne is also an affiliate of the Beckman Institute for Advanced Science and Technology at Illinois.

The U.S. Army Corps of Engineers' Construction Engineering Research Laboratory, National Science Foundation and the Japanese Ministry of Education, Culture, Sports, Science, and Technology supported this research.

Editor's notes:

To reach Marianne Alleyne, call 217-333-8652; email
vanlaarh@illinois.edu.

To reach Jessica Román-Kustas, email jkkusta@sandia.gov.

The paper "Molecular and topographical organization: Influence on cicada wing wettability and bactericidal properties" is available U. of I. News Bureau.

University of Illinois at Urbana-Champaign, News Bureau

Related Biological Structures Articles from Brightsurf:

Norovirus has two alternative capsid structures which change before infection
Researchers from the National Institute for Physiological Sciences have discovered that mouse noroviruses have two alternative capsid structures and change from one to the other before infection.

RNA structures by the thousands
Researchers from Bochum and M√ľnster have developed a new method to determine the structures of all RNA molecules in a bacterial cell at once.

Blocking sugar structures on viruses and tumor cells
During a viral infection, viruses enter the body and multiply in its cells.

Harnessing the domino effect for deployable structures
A team of researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have harnessed the domino effect to design deployable systems that expand quickly with a small push and are stable and locked into place after deployment.

A new approach to reveal the multiple structures of RNA
The key of the extraordinary functionality of ribonucleic acid, better known as RNA, is a highly flexible and dynamic structure.

How human social structures emerge
What rules shaped humanity's original social networks? The earliest social networks were tightly knit cultural groups made of multiple biologically related families.

Structures in seaweed shed light on sustainability
By examining the enzymes that break down the alginate, the researchers from China and the United Kingdom may be able to harness the natural process to produce biofuel.

A laser, a crystal and molecular structures
Researchers have built a new tool to study molecules using a laser, a crystal and light detectors.

Optimizing structures within complex arrangements of bubbles
New research published in EPJ E explores how different numbers of 2D bubbles of two different areas can be arranged within circular discs, in ways which minimize their perimeters.

A new way of making complex structures in thin films
Self-assembling materials called block copolymers, which are known to form a variety of predictable, regular patterns, can now be made into much more complex patterns that might someday be useful for making optical or plasmonic devices (in which electromagnetic waves interact with electrons), according to an MIT study.

Read More: Biological Structures News and Biological Structures Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.