MMaterialsgateNEWS 2017/11/06

Related MaterialsgateCARDS

Synthetic material acts like an insect cloaking device

Credit: Shikuan Yang / Birgitt Boschitsch / Penn State

Synthetic microspheres with nanoscale holes can absorb light from all directions across a wide range of frequencies, making them a candidate for antireflective coatings, according to a team of Penn State engineers.

The synthetic spheres also explain how the leaf hopper insect uses similar particles to hide from predators in its environment.

Scientists have long been aware that leaf hoppers extrude microparticles, called brochosomes, and wipe them on their wings. Because the particles are superhydrophobic, the leaf hopper's wings stay dry in wet conditions. What was not understood before the current work is that the brochosomes also allow leaf hoppers and their eggs to blend in with their backgrounds at the wavelengths of light visible to their main predators, such as the ladybird beetle.

"We knew our synthetic particles might be interesting optically because of their structure," said Tak-Sing Wong, assistant professor of mechanical engineering and the Wormely Family Early Career Professor in Engineering. "We didn't know, until my former postdoc and lead author of the study Shikuan Yang brought it up in a group meeting, that the leaf hopper made these non-sticky coatings with a natural structure very similar to our synthetic ones. That led us to wonder how the leaf hopper used these particles in nature."

Doing a search of the scientific literature turned up nothing about the leaf-hopper brochosomes' use as camouflage. But the pits' sizes in the synthetic microspheres are very close to the wavelength of light, and can capture up to 99 percent of light, ranging from ultraviolet through visible and into the near infrared. The particle surface acts like a metamaterial, the type of material used in cloaking devices.

"The problem is that in the field, these leaf hoppers produce very little of this product, and it is very hard to collect," Wong said. "But we had already produced large quantities of these structures in the lab, enough to put inside a machine to look at their optical properties."

In a paper published online today (Nov. 3) in Nature Communications, the researchers simulated insect vision and found that the brochosomes are very likely camouflage coatings against leaf hopper predators. Camouflage is common in nature, but there are very few examples of natural antireflective coatings, moth eyes being a prominent exception. Moth eyes are covered in anti-reflective nanostructures that prevent light from reflecting off them at night when predators might see them.

The synthetic microspheres are produced via a rather complex five-step process using electrochemical deposition. However, the process can be scaled up and many different materials can be used to make the synthetic brochosomes, such as gold, silver, manganese oxide or even a conductive polymer.

"Different materials will have their own applications," Wong said. "For example, manganese oxide is a very popular material used in supercapacitors and batteries. Because of its high surface area, this particle could make a good battery electrode and allow a higher rate of chemical reaction to take place."

As an antireflective coating, this material could have applications in sensors and cameras, where capturing unwanted light reflection could increase the signal-to-noise ratio. This also could be particularly useful in telescopes. For solar cell applications, a coating of synthetic brochosomes could increase light capture at multiple wavelengths and from every angle due to the 3D soccer-ball-shaped structure of the spheres, making it unnecessary to build devices to track the sun.

"This paper is more of a fundamental study," Wong said. "In the future, we may try to extend the structure to longer wavelengths. If we made the structure a little larger, could it absorb longer electromagnetic waves such as mid-infrared and open up further applications in sensing and energy harvesting?"

That remains to be studied.

Source: Penn State, Walt Mills – 03.11.2017.

Investigated and edited by:

Dr.-Ing. Christoph Konetschny, Inhaber und Gründer von Materialsgate
Büro für Material- und Technologieberatung
The investigation and editing of this document was performed with best care and attention.
For the accuracy, validity, availability and applicability of the given information, we take no liability.
Please discuss the suitability concerning your specific application with the experts of the named company or organization.

You want additional material or technology investigations concerning this subject?

Materialsgate is leading in material consulting and material investigation.
Feel free to use our established consulting services

MMore on this topic

An electric current will not only heat a hybrid metamaterial, but will also trigger it to change state and fade into the background like a chameleon in what may be the proof-of-concept of the first controllable metamaterial device, or metadevice, according to a team of engineers.

"Previous metamaterials work focused mainly on cloaking objects so they were invisible in the radio frequency or other specific frequencies," said Douglas H. Werner, John L. and Genevieve H. McCain Chair Professor of electrical engineering, Penn State. "Here we are not trying to make something disappear, but to make it blend in with the background like a chameleon and we are working in optical wavelengths, specifically in the infrared." Metamaterials are synthetic, composite materials that possess qualities not seen in natural materials. These composites derive their functionality by their internal structure rather than by their chemical composition. Existing metamaterials... more read more

Invisibility cloaks have less to do with magic than with metamaterials. These human-engineered materials have properties that don't occur in nature, allowing them to bend and manipulate light in weird ways.

For example, some of these materials can channel light around an object so that it appears invisible at a certain wavelength. These materials are also useful in applications such as smaller, faster, and more energy efficient optics, sensors, light sources, light detectors and telecommunications devices. Now researchers have designed a new kind of metamaterial whose properties can be changed with a flick of a switch. In their proof-of-principle experiment, the researchers used germanium antimony telluride (GST) -- the kind of phase-change material found in CDs and DVDs -- to make an improved switchable metasurface that can block or transmit particular wavelengths of light at the command of... more read more

Iowa State University engineers have developed a new flexible, stretchable and tunable "meta-skin" that uses rows of small, liquid-metal devices to cloak an object from the sharp eyes of radar.

The meta-skin takes its name from metamaterials, which are composites that have properties not found in nature and that can manipulate electromagnetic waves. By stretching and flexing the polymer meta-skin, it can be tuned to reduce the reflection of a wide range of radar frequencies. The journal Scientific Reports recently reported the discovery online. Lead authors from Iowa State's department of electrical and computer engineering are Liang Dong, associate professor; and Jiming Song, professor. Co-authors are Iowa State graduate students Siming Yang, Peng Liu and Qiugu Wang; and former Iowa State undergraduate Mingda Yang. The National Science Foundation and the China Scholarship... more read more


Partner of the Week

Search in MaterialsgateNEWS

Books and products