A simple laboratory mistake has unveiled an entirely new world of spontaneous pattern formation that could reshape our understanding of how complex designs emerge in both engineered materials and living systems.
UCLA researchers have discovered that hundreds of identical, intricate spiral patterns can spontaneously etch themselves onto semiconductor surfaces through a previously unknown interaction between chemistry and physical force. The finding, published March 3 in Physical Review Materials, offers scientists a new experimental system for studying pattern formation—the first major advance in this field since the 1950s.
The discovery happened entirely by accident when UCLA doctoral student Yilin Wong left a sample out overnight—a germanium wafer coated with thin metal films in contact with a drop of water. What should have been a ruined experiment instead revealed something extraordinary when she examined it under a microscope.
“I was trying to develop a measurement technique to categorize biomolecules on a surface through breaking and reforming of the chemical bonds,” Wong explained. “Fixing DNA molecules on a solid substrate is pretty common. I guess nobody who made the same mistake I did happened to look under the microscope.”
That fortuitous glance revealed beautiful spiral patterns etched into the germanium surface by a chemical reaction—a completely unexpected outcome that sparked the researchers’ curiosity.
Intrigued by this accidental discovery, Wong and physics professor Giovanni Zocchi systematically investigated what caused these patterns to form. They created a setup where a 10-nanometer thick layer of chromium, followed by a 4-nanometer layer of gold, was evaporated onto a germanium wafer. When exposed to a mild etching solution for 24-48 hours, remarkable patterns emerged.
“The system basically forms an electrolytic capacitor,” Zocchi said.
Their investigation revealed something fascinating: as the chemical reaction progressed, the metal films delaminated from the germanium surface, creating stress that produced wrinkles in the metal. These wrinkles, influenced by further catalytic reactions, ultimately etched the elaborate patterns into the germanium.
The researchers found they could generate different patterns—Archimedean spirals, logarithmic spirals, lotus flower shapes, and more—simply by adjusting experimental parameters like the thickness of the metal film.
“The thickness of the metal layer, the initial state of mechanical stress of the sample, and the composition of the etching solution all play a role in determining the type of pattern that develops,” Zocchi noted.
What makes this discovery particularly significant is that the patterns aren’t purely chemical in origin. They emerge from the interaction between chemistry and mechanical forces—specifically, the residual stress in the metal film determines the shapes that form. This coupling between chemical reactions and mechanical deformation is rare in laboratory settings but common in nature.
The researchers point out that the process bears striking similarities to biological growth, where enzymes catalyze growth that deforms cells and tissue into particular shapes, some resembling those observed in Wong’s experiments.
“In the biological world, this kind of coupling is actually ubiquitous,” Zocchi explained. “We just don’t think of it in laboratory experiments because most laboratory experiments about pattern formation are done in liquids. That’s what makes this discovery so exciting. It gives us a non-living laboratory system in which to study this kind of coupling and its incredible pattern-forming ability.”
The patterns observed in these experiments mirror theoretical dynamics first proposed by British mathematician Alan Turing in the 1950s, who discovered that chemical systems could spontaneously form patterns like stripes or polka dots.
Pattern formation in chemical reactions has been studied since 1951, when Soviet chemist Boris Belousov accidentally discovered a chemical system that could spontaneously oscillate in time. This discovery launched the fields of chemical pattern formation and nonequilibrium thermodynamics.
However, despite significant theoretical advances, the experimental systems used to study chemical pattern formation have changed little since those introduced seven decades ago. The Wong-Zocchi system represents the first major experimental advance in this field in generations.
The potential applications extend beyond pure scientific curiosity. Understanding how stress influences pattern formation could help researchers better grasp phenomena ranging from crack formation in engineered materials to growth patterns in biological systems.
For now, Wong and Zocchi continue to explore the parameters that influence these patterns, hoping to uncover the fundamental rules governing how complex designs emerge from simple chemical and mechanical interactions—a question that has fascinated scientists since the dawn of modern chemistry and may now be answerable in new ways thanks to a fortunate laboratory mistake and the curiosity to investigate it.
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