Whiteflies, a common insect, secrete tiny, mysterious particles that could be both inspiration and instructions for next-generation technology, according to a new study led by researchers in Pennsylvania. The team first accurately recreated the complex geometry of these particles, called brochiosomes, and gained a better understanding of how they absorb both visible and ultraviolet light.

This could enable the development of bio-inspired optical materials, with possible applications from invisible cloaking devices to coatings for more efficient solar energy harvesting, said Tak-Sing Wong, professor of mechanical and biomedical engineering. Wong led the study, published today (March 18) in the Proceedings of the National Assembly. National Academy of Sciences United States of America (PNAS).

The mystery of brooches revealed

The uniquely small particles have an unusual football-like geometry and spacing, and their precise purpose for insects has been a mystery to scientists since the 1950s. In 2017, Wong led a Penn State research team that was the first to create a basic synthetic version of brochiosomes to better understand their function.

“This discovery could be very useful for technological innovation,” said Lin Wang, a doctoral student in mechanical engineering and lead author of the study. “Thanks to a new strategy for regulating the reflection of light on a surface, we will be able to hide the thermal signatures of humans or machines. Perhaps one day humans will be able to develop a thermal invisibility cloak based on the tricks used by leafhoppers. Our work shows how understanding nature can help us develop modern technologies.”

Wang went on to explain that although scientists have known about broccosome particles for three-quarters of a century, it is difficult to make them in the laboratory due to the complexity of the particles’ geometry.

Brochosome conception and replication

“It was not clear why the locusts produced particles with such complex structures,” Wang said. — We managed to produce these brochiosomes in the laboratory using the high-tech 3D printing method. We found that these lab-made particles can reduce light reflection by up to 94%. “This is a big discovery because it’s the first time we’ve seen nature do something like this, controlling light in such a specific way with hollow particles.”

Theories about why leafhoppers cover themselves in brochosomal armor range from protection from pollution and water to a superhero-like invisibility cloak. However, the new understanding of their geometry raises the possibility that their primary purpose was a cloak for protection from predators, according to Tak-Sing Wong, professor of mechanical engineering and biomedical engineering and corresponding author of the study.

The researchers found that the size of the holes in the broccossode, which gives it its hollow, football-like appearance, is extremely important. Regardless of the size of the insect’s body, the size is the same for different species of leafminers. Brochiosomes are about 600 nanometers in diameter (about half the size of a bacterium), and the pores of brochiosomes are about 200 nanometers.

“This allows us to ask questions,” Wong said. “Why such a sequence? What is the secret of having brochiosomes that are about 600 nanometers in size and have pores of about 200 nanometers? Does it serve any purpose?”

Potential applications and future directions

The researchers discovered that the brochiosomes’ unique design serves the dual purpose of absorbing ultraviolet (UV) light, which reduces visibility to UV-visioned predators such as birds and reptiles, and creating an anti-glare shield against potential threats by scattering visible light. The size of the holes is ideal for absorbing UV light.

The researchers say this could potentially lead to a variety of applications, such as more efficient solar energy harvesting systems for humans using synthetic brochiosomes, coatings that protect pharmaceutical products from light damage, improved sunscreens to better protect skin from sun damage, and even camouflage devices. . . To test this, the team first needed to make synthetic brochiosomes; This in itself was a huge challenge.

In their study in 2017, researchers mimicked some of the features of brochiosomes, including their pits and distribution, using synthetic materials. This allowed them to begin to understand optical properties. However, they were only able to make something similar to brochiosomes, not an exact replica.

Wong explained that researchers were able to create large-scale synthetic copies of broccolosome structures using advanced 3D printing technology, saying, “This is the first time we can create the exact geometry of a natural broccolosome.”

They printed an enlarged version that was 20,000 nanometers in size, about one-fifth the diameter of a human hair. The researchers precisely reproduced the shape and morphology, number and position of the pores using 3D printing to produce small artificial brochiosomes that are still large enough to be identified optically.

They used a micro-Fourier transform infrared (FTIR) spectrometer to examine how brochiosomes interact with different wavelengths of infrared light, helping researchers understand how the structures manipulate light.

The researchers next stated that they plan to improve the production of synthetic broschiosomes to enable production at a scale closer to the size of natural broschiosomes. They will also explore additional applications for synthetic broschiosomes, such as information encryption, where broschiosome-like structures could be used as part of an encryption system where data is visible only in certain wavelengths of light.

Wang said their work with brochiosomes demonstrates the value of the biomimetic research approach, where scientists look to nature for inspiration.

“Nature has been a good teacher for scientists in developing new advanced materials,” Wang said. “We focused on just one type of insect in this study, but there are many more surprising insects waiting for scientists to discover, and they could help us solve a variety of engineering problems. These aren’t just bugs; they’re a source of inspiration.”