Backyard leafhoppers inspire next-generation cloaking tech

From Harry Potter to The Lord of The Rings, tall tales regale us with the potential benefits of invisibility. Many researchers would like to bring such benefits to the real world. One new tech might allow some things to practically hide in plain sight. Its inspiration: the common backyard leafhopper.

A camouflage artist, this insect is an expert nanoengineer.

An adult leafhopper coats its body with a liquid. That goo is filled with tiny, complex nanospheres. These anti-reflective, soccer-ball-shaped objects are called brochosomes (BROK-ih-zoams). As light hits them, they change its behavior, explains Roman Rakitov. He works at the Russian Academy of Sciences in Moscow. An insect biologist, he did not work on the new study.

Those brochosomes cut the reflection of both visible and ultraviolet (UV) light. Instead of being shiny and eye-catching, the leafhopper becomes rather dull — like its surroundings. Something that reflects little to no light can become nearly invisible. So those nanostructures in the leafhopper’s coat make it “less visible to some predators,” explains Rakitov. That’s especially true for predators that see only in UV, such as some birds and insects.

Researchers at Penn State University in State College have now developed a technique to mass-produce synthetic brochosomes. They say these structures might one day pave the way to next-gen camouflage and anti-reflective coatings.

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Natural cloaking tech cuts glare

Engineers often draw inspiration from nature for cloaking and other camouflage techniques. Some fish, for instance, reflect polarized light to hide in the open ocean. Glasswing butterflies use waxy bumps on their wings to reflect less light. Tak-Sing Wong wondered if he could cloak things by coating them with brochosomes.

A mechanical engineer, Wong works at Penn State. He saw potential in brochosomes for making anti-reflective paints and other coatings.

Through a microscope, brochosomes resemble tiny balls with hollow centers. A honeycomb grid of holes covers their surface. When Wong first saw a picture of them, he thought they must be human-made. “How on Earth can a simple insect make such a complex structure?” he recalls wondering.

He suspected that 3-D structure was key to a brochosome’s ability to fight glare. But copying its structure proved tricky. Each sphere is less than one-millionth of a meter across. (It would take 70 of these balls lined up to match the width of a single human hair.)

In 2024, Wong’s team used a 3-D printing method to re-create the shape of these complex balls. They designed ones with holes of different shapes and sizes. Then they tested which of them reflected the least light. 

Alas, their 3-D printing method wouldn’t easily make large amounts of these balls. And without that, the tech would not be practical for real-world use.

Once again, Wong’s team turned to the leafhoppers for inspiration.

How to make molecules assemble

Leafhoppers make their brochosomes in specialized organs. Called Malpighian (Mal-PIG-ee-un) tubules, they’re part of the insect’s waste-removal system. One part of this organ secretes proteins and fatty molecules called lipids.

Those molecules later come together on their own, says Elizabeth Bello. The proteins and lipids first join to make a round blob. Holes and pits then develop on its surface. Scientists don’t yet know the exact chemistry that drives this shaping, Bello adds.

The biologist did not take part in this new study. But she does appreciate it. Her lab studies brochosomes at the University of Illinois Urbana-Champaign.

To mimic the ball-making process in leafhoppers, Wong’s team turned to microfluidics. This field of research involves the precise control of very small amounts of fluid.

Their fluid contained a mix of what are called amphiphilic (Am-fih-FIH-lik) molecules. They contain some parts that are attracted to water; other parts are drawn to oil. These molecules mimic the proteins and lipids that make natural brochosomes. And under the right conditions, they similarly self-assemble into 3-D structures.

Wong’s group created special oil droplets. Each droplet had a bit of water trapped inside. This encourages the amphiphilic molecules to organize themselves within the droplets. The oil-loving parts tended to stick to the oily side of the droplets. The water-loving parts moved toward the water.

In this way, polymers gathered at the droplet’s edge. They formed a neat layer. Here, they also self-assembled into honeycomb shapes that mimic brochosomes. Once they hardened, they even exhibited geometry and surface patterns that looked like the leafhoppers’.

To test their particles’ anti-reflective traits, Wong’s group coated different surfaces with these lab-made brochosomes. And this coating effectively reduced glare and reflection, they now report. The team shared details of it last December in ACS Nano. 

The particles cut glare from any viewing angle. That’s an advance over current anti-reflective coatings. Most others work best only when viewed from a certain angle. Many smartphone screens, for instance, have a privacy feature. It makes the screen appear blank when you glance at it from the side. But from the front, the screen is visible.

One major advance, Wong says, was his team’s ability to tightly control how their particles formed. They could adjust the mix of molecules and how big the droplets were. Such tweaks would coax the structures to take on slightly different shapes. Some might get thicker walls. Others got larger holes. Importantly, their microfluidic system could pump out droplets extremely fast — 100,000 or more each second!

“I was really excited to read [this study],” says Bello. A small handful of research groups have recently made brochosome-like materials, she notes. “But they could only be produced in limited quantities,” she says. “Having a method to mass-produce brochosome-like particles is a significant breakthrough.”

Wong says his team’s work has many potential applications. Eyeglass lenses, solar panels and other optical surfaces are often coated to reduce glare or reflection. The faux brochosomes might work even better than those. Anti-glare tech has also found use in military gear and self-cleaning surfaces.