Scientists may be a step closer to creating a Harry Potter-style invisibility cloak. The key: microparticles sweated out by leafhopper insects.
These particular microparticles are called brochosomes and their function is to keep the insects' wings dry in wet conditions, which they do by repelling water.
Now, engineers from Penn State University have discovered that the brochosomes also provide leafhoppers with camouflage, keeping the little bugs and their eggs hidden from predators by altering the wavelengths of light. Effectively, they work like a cloaking device.
"We knew our synthetic particles might be interesting optically because of their structure," Tak-Sing Wong, assistant professor of mechanical engineering and the Wormely Family Early Career Professor in Engineering at Penn State, explained in the statement.
"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 leafhopper made these non-sticky coatings with a natural structure very similar to our synthetic ones. That led us to wonder how the leafhopper used these particles in nature."
In a study published last week in Nature Communications, the engineers designed a synthetic material that mimicked the properties of the leafhopper's brochosomes using a complicated five-step process, which involved something called electrochemical deposition.
The researchers then tested these artificial brochosomes by putting them on leaves and watching them with simulated insect vision. The synthetic particles captured up to 99 percent of light across the spectrum (from ultraviolet to visible to near infrared) and successfully blended into the background.
The synthetic brochosomes could be made from various different materials, from metals like gold and silver to compounds like manganese oxide. Each of these materials would have their own purpose and applications, the researchers 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," explained Wong.
Other uses suggested include an anti-reflective coating for sensors and cameras, where light reflection increases the signal-to-noise ratio, and solar cells to increase light capture at different wavelengths and angles.
This is a "fundamental study", Wong pointed out. "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?"
So if you're waiting for an invisibility cloak, it's best not to hold your breath.
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