One night, UCLA doctoral student Yilin Wong left a sample out by mistake.
It was a small chip made of germanium, topped with thin layers of metal, and had a drop of water on it.
The next day, she noticed tiny dots had formed on the surface. Curious, she looked at them under a microscope—and was stunned.
Beautiful spiral patterns had formed on the chip, etched into the surface like tiny works of art.
This accidental discovery led Wong on an exciting journey.
Working with UCLA physics professor Giovanni Zocchi, she found that hundreds of spiral patterns could form all by themselves on a small germanium chip, just one centimeter wide.
Even more amazing, by changing small details—like how thick the metal layers were—they could create different shapes: perfect spirals, flower-like patterns, and other symmetrical designs.
Their experiment involved coating a germanium chip with a 10-nanometer layer of chromium and a 4-nanometer layer of gold.
Then, they added a mild etching solution and let it sit overnight. After washing it, they added more solution in a humid environment to keep it from drying out.
The metal layers acted like an electrolytic capacitor, and over a day or two, a chemical reaction etched patterns into the germanium surface.
As the reaction continued, the metal layers—under built-up stress—started to peel away in places. This stress caused the layers to wrinkle, and these wrinkles helped shape the beautiful designs seen under the microscope.
What made this discovery truly unique is how it combined chemistry and mechanics.
It wasn’t just the chemical reaction creating the shapes—the stress in the metal layers also played a big role. The researchers found that the type of pattern depended on factors like the stress in the metal, how thick it was, and the makeup of the etching solution.
Interestingly, this kind of pattern-making process is common in nature.
For example, enzymes help tissues grow into shapes during development, often guided by similar forces. But in the lab, scientists rarely see this combination of chemical and mechanical effects.
The discovery adds a whole new way to study pattern formation, a field that began in the 1950s. It also opens the door to exploring how stress and chemistry together can create complex designs—just like in living things, but in a completely non-living system.
