Leafhopper on leaf
Pictured is a leafhopper G. serpenta. Lin Wang et al. studied the geometric designs of the surface coatings on leafhopper bodies. Leafhoppers produce brochosomes to coat their body surfaces, which are hollow, nanoscopic, buckyball-shaped spheroids with through-holes distributed across their surfaces. The authors found that the through-holes of these hollow buckyballs play an important role in reducing the reflection of light. This is the first biological example showing short wavelength, low-pass antireflection functionality enabled by through-holes and hollow structures. (Credit: Lin Wang and Tak-Sing Wong/Penn State)
UNIVERSITY PARK, Pa. — In the miniature world of insects, survival often depends on staying hidden from predators. While some creatures rely on camouflage patterns or colors to blend in with their surroundings, leafhoppers have developed a unique and fascinating method of concealment. These small, plant-dwelling insects coat themselves with microscopic spheres called brochosomes, which act as a remarkable form of invisibility cloak. Now, researchers have uncovered the secrets behind these tiny orbs’ ability to manipulate light, potentially inspiring new technologies for everything from anti-reflective coatings to advanced camouflage.
Leafhoppers, relatives of cicadas, are found worldwide and play important roles in ecosystems as both plant-eaters and prey for other animals. What makes them special is their ability to produce and apply brochosomes to their bodies. These hollow, soccer ball-like structures are so small that hundreds could fit across the width of a human hair. Scientists have known about brochosomes since the 1950s, but their exact purpose remained a mystery – until now.
A team led by researchers from Pennsylvania State University and Carnegie Mellon University has cracked the code of how brochosomes work their optical magic. Their findings, published in the Proceedings of the National Academy of Sciences, reveal that these minuscule spheres are precisely engineered by nature to reduce light reflection across a wide range of wavelengths, including ultraviolet (UV) light that many insect predators can see.
“This discovery could be very useful for technological innovation. With a new strategy to regulate light reflection on a surface, we might be able to hide the thermal signatures of humans or machines,” says lead author Lin Wang, a postdoctoral scholar in mechanical engineering at Penn State, in a statement. “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.”
Pictured are brochosomes produced by leafhopper G. serpenta. Brochosomes are hollow, nanoscopic, buckyball-shaped spheroids with through-holes distributed across leafhoppers’ body surfaces. Lin Wang et al. studied the relationship between the optical properties and the geometric designs of the brochosomes. The authors found that the through-holes of these hollow buckyballs play an important role in reducing the reflection of light. This is the first biological example showing short wavelength, low-pass antireflection functionality enabled by through-holes and hollow structures. (Credit: Lin Wang and Tak-Sing Wong/Penn State)
The key to the brochosomes’ effectiveness lies in their size and structure. Most brochosomes measure about 600 nanometers in diameter – about half the size of a single bacterium – with tiny holes covering their surface that are around 200 nanometers wide. These dimensions aren’t random – they’re perfectly tuned to interact with light in ways that make the leafhopper less visible.
The researchers found that brochosomes work through two main mechanisms. First, their overall size is just right to cause something called Mie scattering. This effect occurs when a particle is about the same size as the wavelength of light hitting it. Instead of reflecting light like a mirror, the particle scatters it in many directions, reducing the amount that bounces directly back to an observer. This is why brochosomes are effective at reducing reflection across a broad range of visible light wavelengths.
However, the real innovation comes from the tiny holes that perforate each brochosome. These act like miniature light traps for shorter wavelengths, particularly in the UV range. When UV light enters these holes, it tends to bounce around inside the hollow sphere rather than escaping back out. This extra level of light absorption is crucial because many insects and birds that prey on leafhoppers can see into the UV spectrum, unlike humans.
“We found that these lab-made particles can reduce light reflection by up to 94%,” says Tak-Sing Wong, a professor of mechanical engineering and biomedical engineering and corresponding author of the study. “This is a big discovery because it’s the first time we’ve seen nature do something like this, where it controls light in such a specific way using hollow particles.”
To better understand how brochosomes work, the research team created artificial versions using advanced 3D printing technology. By scaling up the structures and testing them with longer wavelengths of infrared light, they could observe and measure the light-manipulating effects in detail. This marks a significant advancement from their 2017 study, where they could only create approximate replicas of brochosomes.
Pictured is an array of 3D printed microscale synthetic brochosome. In nature, leafhoppers produce brochosomes to coat their body surfaces, which are hollow, nanoscopic, buckyball-shaped spheroids with through-holes distributed across their surfaces. Lin Wang et al. studied the relationship between the optical properties and the geometric designs of the brochosomes utilizing 3D printed synthetic brochosomes. The authors found that the through-holes of these hollow buckyballs play an important role in reducing the reflection of light. This is the first biological example showing short wavelength, low-pass antireflection functionality enabled by through-holes and hollow structures. (Credit: Lin Wang and Tak-Sing Wong/Penn State)
“This is the first time we are able to make the exact geometry of the natural brochosome,” Wong explains.
The team used a technique called two-photon polymerization 3D printing to create synthetic brochosomes that were about 20,000 nanometers in size – roughly one-fifth the diameter of a human hair. While still tiny, these were large enough to study in detail using specialized equipment.
The consistency of brochosome size across different leafhopper species, regardless of the insect’s overall body size, suggests that evolution has honed in on this optimal design for light manipulation. By reducing reflection across both visible and UV light, leafhoppers can better blend in with the leaves they live on, which naturally absorb UV light.
This research isn’t just about understanding nature’s clever designs – it could lead to new technologies inspired by brochosomes. Anti-reflective coatings based on this principle could improve solar panels, camera lenses, or displays. The ability to selectively absorb certain wavelengths while scattering others could be useful for creating advanced camouflage materials or even in optical computing and communication.
Pictured is a leafhopper G. serpenta. Lin Wang et al. studied the geometric designs of the surface coatings on leafhopper bodies. Leafhoppers produce brochosomes to coat their body surfaces, which are hollow, nanoscopic, buckyball-shaped spheroids with through-holes distributed across their surfaces. The authors found that the through-holes of these hollow buckyballs play an important role in reducing the reflection of light. This is the first biological example showing short wavelength, low-pass antireflection functionality enabled by through-holes and hollow structures. (Credit: Lin Wang and Tak-Sing Wong/Penn State)
“Nature has been a good teacher for scientists to develop novel advanced materials,” says Wang. “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.”
As we continue to unravel nature’s ingenious solutions to complex problems, the humble leafhopper reminds us that sometimes the most remarkable innovations come in the tiniest packages. These insects, armed with their coat of invisibility spheres, demonstrate how evolution can produce sophisticated optical engineering at the nanoscale. By learning from and mimicking these natural designs, we may develop new ways to control and manipulate light for a wide range of applications, all thanks to a small bug’s big discovery in staying hidden.
Paper Summary
Methodology
The researchers used a combination of advanced techniques to study brochosomes and create artificial versions for testing. They examined natural brochosomes using powerful electron microscopes to understand their structure in detail. To create synthetic brochosomes, they used a technique called two-photon polymerization 3D printing, which allows for the creation of extremely small and precise structures.
These artificial brochosomes were made larger than natural ones, about 20,000 nanometers in size, or roughly one-fifth the diameter of a human hair. The team then used a Micro-Fourier transform infrared (FTIR) spectrometer to examine how the brochosomes interacted with infrared light of different wavelengths, helping them understand how the structures manipulate light.
Key Results
The study found that brochosomes reduce light reflection through two main mechanisms. First, their overall size (about 600 nm) causes Mie scattering, which reduces reflection across a broad range of visible light wavelengths. Second, the holes in the brochosomes (around 200 nm in diameter) act as traps for shorter wavelengths, particularly UV light.
Combined, these effects can reduce light reflection by up to 94% compared to a flat, reflective surface. The researchers also found that the size and structure of brochosomes are remarkably consistent across different leafhopper species, suggesting an evolutionarily optimized design.
Study Limitations
While the study provides significant insights, there are some limitations. The experiments were conducted using scaled-up synthetic brochosomes and infrared light, which may not perfectly replicate the behavior of natural brochosomes with visible and UV light. Additionally, the study focused on the physical properties of brochosomes and their interaction with light, but did not directly test their effectiveness in camouflaging leafhoppers in natural settings. The biological materials that make up natural brochosomes may have additional properties not captured by the synthetic versions.
Discussion & Takeaways
This research reveals that brochosomes are a sophisticated example of natural optical engineering. Their dual mechanism for reducing light reflection – Mie scattering and wavelength-specific absorption – represents a unique approach in nature. This design allows leafhoppers to reduce their visibility across a wide range of wavelengths, including UV light that many of their predators can see. The consistency of brochosome size across different leafhopper species suggests strong evolutionary pressure to maintain this optimal design.
The findings have potential applications in various fields. The brochosome design could inspire new anti-reflective coatings for solar panels, camera lenses, or displays. The ability to selectively absorb certain wavelengths while scattering others could be useful in developing advanced camouflage materials, thermal invisibility cloaks, or optical computing technologies. The researchers are already exploring additional applications, such as using brochosome-like structures for information encryption systems where data is only visible under certain light wavelengths.
This study also highlights the value of biomimicry – learning from and imitating nature’s designs to solve human problems. By understanding how leafhoppers use these nanostructures to manipulate light, we may develop new ways to control and use light in various applications, from improving energy efficiency to enhancing optical communications. As the researchers continue to refine their techniques for creating synthetic brochosomes closer to the size of natural ones, we can expect even more exciting developments in this field of bioinspired materials.