When most people see a leafhopper in their backyard garden, they notice little more than a tiny green or striped insect flicking from leaf to leaf. But these insects are actually master engineers, capable of building some of the most complex natural nanostructures known, which makes them invisible to many of their predators. Their secret lies in brochosomes: tiny, hollow nanostructures that leafhoppers naturally produce and coat themselves with. A team at Penn State has now developed a high-speed platform capable of producing synthetic versions of brochosomes at a rate exceeding 100,000 per second, a technological achievement that could lead to next-generation camouflage, sensors and other advancements for humans.
They published their work today (Dec. 12), in ACS Nano.
"Each brochosome is smaller than a speck of pollen yet has astonishingly intricate architecture, looking like a perfectly patterned soccer ball covered with nanoscale pores," said Tak-Sing Wong, professor of mechanical engineering and biomedical engineering.
Awarded little attention outside entomology circles, leafhopper brochosomes have fascinated scientists because of their complexity and optical behavior. The unique design of brochosomes serves a dual purpose. One is absorbing ultraviolet (UV) light, which reduces visibility to predators with UV vision, such as birds and reptiles, because the hole size is perfect for absorbing light at the UV frequency. They also scatter visible light, creating an anti-reflective shield against potential threats - it's so effective that their wings appear nearly non-reflective, offering natural camouflage from predators.
This insect trickery inspired Wong and his research team, who previously mimicked the intricate nanostructure of brochosomes to manufacture synthetic versions, but at a limited scale. Now, the team's new platform can produce synthetic brochosomes at an estimated rate of 140,000 particles per second - a productivity leap that could finally make the synthetic version of these particles practical for real-world technologies, Wong said.
Co-author Jinsol Choi, postdoctoral scholar in Wong's lab group, explained that because many potential applications - from non-reflective surfaces for invisibility cloaks to high-surface-area catalysts and sensing materials - require massive quantities of precisely engineered nanoparticles, the ability to mass-produce these complex structures at high speed brings them much closer to commercial use.
"Our group has been working on synthetic brochosomes for almost a decade," said Wong, who is also part of the Materials Research Institute, co-authored the study outlining the work along with Choi. "The advance marks a significant step forward from our group's earlier efforts, which first demonstrated the potential of brochosomes to manipulate light. The new study not only recreates their complex architecture but also shows how to manufacture them with unprecedented precision and scale. Until now, humans could not reproduce these structures at comparable scales or complexity. Their fully 3D geometry and nanoscale features pushed beyond what even our most advanced fabrication tools could reliably create."
The team began their latest achievement by looking closely at how leafhoppers themselves make brochosomes. Inside the insect's Malpighian tubules, a type of internal plumbing system, droplet-like condensates develop surface ripples, where proteins and lipids in the system undergo self-assembly to form brochosome structures.
"Nature is the master of nanomanufacturing," Wong said. "Leafhoppers build brochosomes not by carving or sculpting them, but through molecular self-assembly and interfacial phenomena."
Choi led the effort to develop a synthetic version of this biological assembly line. The team used a tiny chip with microscopic channels that create identical droplets, each containing specially designed polymers made to either repel or attract water. The polymers are distributed both at the surface and within the droplet, so when the droplet evaporates, additional polymers migrate toward the surface. As this happens, these parts arrange themselves on the droplet's surface, naturally creating the tiny, evenly spaced pores that give brochosomes their unique structure.
"The chemistry of the polymer determines how the droplet surface bends," Choi said. "The bending controls how water infiltrates, and the arrangement of those infiltrated droplets sets the size and shape of the pores."
By adjusting polymer composition, molecular length and droplet size, the researchers were able to tune the geometry of the final particles and recreate brochosomes similar to those produced by different leafhopper species.
The synthetic particles also display the same optical behavior as natural brochosomes. When the team coated surfaces with their particles, they observed a strong reduction in reflected light across different wavelengths and angles. The performance is difficult to achieve with conventional antireflective coatings, which typically work only at specific angles or within narrow bands of light, according to Wong.
"Many technologies rely on careful control of light," Wong said. "Cameras and sensors that struggle with glare, solar panels that lose efficiency when light bounces away, or defense optics that need reliable antireflection to make themselves 'invisible,' these all could benefit from materials that reduce reflections so strongly."
Beyond optics, the particles' hollow structure and high internal surface area suggest potential opportunities in energy and chemical research, the researchers said. Their porous shells may inspire future exploration in areas such as catalysis or energy-storage materials. In other fields, the particles' unique shape and light-scattering behavior could open up new possibilities for pigments, camouflage coatings, or chemical and biological sensing technologies.
"Synthetic brochosomes combine several unusual features; they're hollow, packed with tiny pores, have a large surface area and function the same from any viewing angle," Wong said. "Their potential goes well beyond reducing glare."
Medical applications may also be possible, Wong noted, explaining that, as the hollow, porous structure of the particles could inspire future research into drug delivery or imaging-related materials.
"Overall, synthetic brochosomes are not just optical materials," Choi said. "They're a versatile new platform that could impact fields from clean energy and pigments to protective coatings and medical technologies."
What truly distinguishes the new platform is its speed, Choi said. Traditional methods of nanofabrication may produce only a few particles per second, often requiring multiple complex steps. This system, by contrast, leverages self-assembly to generate more than 100,000 fully formed particles every second.
"Because the structure essentially builds itself from the bottom up, we achieve both nanoscale precision and extremely high production speed, mimicking how biology constructs nanoscale architectures," Wong said. "This level of detail and throughput simply isn't achievable using conventional approaches."
Next, the researchers plan to further scale up the microfluidic platform, increasing the production rate by 10 to 1,000 times, and investigate optical applications as pigments as well as potential military applications.
A patent application for the technology has been filed. The U.S. Office of Naval Research supported this research.
