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Leafhoppers, which are found around the world, coat themselves in particles known as brochosomes. The study by researchers at Pennsylvania State University (Penn State) replicated the complex geometry of the particles, and studied how they absorb visible and ultraviolet (UV) light.
That understanding could enable the development of bioinspired optical materials with applications ranging from cloaking devices to coatings for more efficient solar energy, said study leader Tak-Sing Wong, professor of mechanical engineering and biomedical engineering.
The tiny particles have an unusual football-like geometry with cavities. Their exact purpose was “something of a mystery” since the 1950s, the university announcement said, but in 2017 Wong led a research team that created a basic, synthetic version to better understand their function.
Making them in a lab was a challenge due to the complexity of the particle’s geometry, said Lin Wang, lead author of the new study. “It has been unclear why the leafhoppers produce particles with such complex structures,” he said.
“We managed to make these brochosomes using a high-tech 3D printing method in the lab. We found that these lab-made particles can reduce light reflection by up to 94%.”
The researchers found that the size of the holes in the brochosome is extremely important. The size is consistent across leafhopper species, no matter the size of the insect’s body. The brochosomes are roughly 600nm (nanometres) in diameter – about half the size of a single bacterium – and the pores are about 200nm.
The size of the holes is perfect for absorbing light at the UV frequency, which reduces visibility to predators with UV vision, and scattering visible light, which creates an ‘anti-reflective shield’.
“This discovery could be very useful for technological innovation,” said Lin Wang. “With a new strategy to regulate light reflection on a surface, we might be able to hide the thermal signatures of humans or machines. Perhaps someday people could develop a thermal invisibility cloak based on the tricks used by leafhoppers. Our work shows how understanding nature can help us develop modern technologies.”
The team printed scaled-up 20,000nm brochosomes, roughly one-fifth the diameter of a human hair. They aim to improve the manufacturing process to enable production closer to the natural size. They also plan to explore additional applications, such as information encryption, where brochosome-like structures could be used as part of an encryption system where data is only visible under certain light wavelengths.
“Nature has been a good teacher for scientists to develop novel advanced materials,” Lin Wang said. “In this study, we have just focused on one insect species, but there are many more amazing insects out there that are waiting for material scientists to study, and they may be able to help us solve various engineering problems. They are not just bugs – they are inspirations.”
The work was published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS).
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