Scientists develop optical metamaterial for vivid, long-lasting colors

Have you ever wondered why a peacock's tail shimmers with brilliant blues and greens, or why a butterfly's wings flash colors that never fade? These are not paints or dyes, but "structural colors" — hues created entirely by microscopic structures that trap, bend and scatter light.

For years, scientists have sought to mimic nature's approach to produce vivid, long-lasting colors for applications ranging from anti-counterfeiting labels to flexible displays. Now, researchers have moved one step closer by developing a new type of optical metamaterial that allows more precise control over microscopic architecture, along with a production method as fast and inexpensive as printing a newspaper. Their findings were published in the journal Nature on Wednesday.

An optical metamaterial can be understood as a tailor-made "fabric for light." Unlike traditional materials, which rely on natural properties — such as stained glass producing colors through refraction — scientists design artificial structures at scales smaller than a strand of hair. These building blocks, typically arranged in repeating grids or pillars, can manipulate the phase, polarization and propagation of light in ways that go beyond the limits of natural materials.

One key application is structural coloration, in which microscopic patterns are tuned to produce a wide range of colors without pigments. This can lead to fade-resistant paints, secure holograms and energy-efficient displays. Beyond color, optical metamaterials are widely regarded as a foundational technology for advances in next-generation optics, communications, high-end manufacturing and military defense.

However, most previous research focused on single-scale structures — like having only one instrument in an orchestra — leaving many properties of light poorly controlled. Manufacturing also required precision tools such as electron beam lithography, which is slow and costly. Producing a sample as small as a fingernail could take days, limiting these materials largely to laboratory settings.

Now, a research team from the Chinese Academy of Sciences and the National University of Singapore addresses the longstanding trade-off of high quality, customization and low cost.

The team designed a new multiscale structure — a microscale hemispherical dome built from periodic nanoscale crystal lattices. This dual-scale structure works like a symphony orchestra: different physical effects interact to control different properties of light, giving scientists a far richer set of "control knobs". Notably, the combination of multiple effects produces a synergy in which the whole is greater than the sum of its parts.

The researchers also developed a roll-to-roll nanoprinting system. It operates on the same continuous, high-speed principle used to print newspapers and magazines: a flexible plastic sheet unspools from one roller, passes through a high-precision printer that deposits nanoscale patterns, and then rolls up on the other side — finished.

Using this method, the team scaled the material from millimeter-sized test pieces to meter-wide sheets — a thousandfold increase — without losing quality.

Nature reviewers praised the breakthrough, noting that the printing strategy is novel and attractive.

Song Yanlin, the study's corresponding author and a researcher at the Institute of Chemistry of the Chinese Academy of Sciences, said the work represents a deep integration of materials science, micro-nano optics and advanced manufacturing.

"Our roll-to-roll nanoprinting technology makes producing optical metamaterials as simple and efficient as printing a newspaper or a book," Song said. "It not only breaks down the high-cost barrier and boosts production efficiency, but also allows us to tailor the optical properties of each individual metamaterial pixel on demand, opening entirely new possibilities for customized micro-nano optics research."

Li Kaixuan, the study's first author and a PhD graduate of the Institute of Chemistry, said a metamaterial film measuring 1 meter in length and 30 centimeters in width can be printed in just 10 minutes. The polystyrene nanoparticle functional ink required to produce a material of this size uses only 1 milliliter, demonstrating high efficiency, with a cost of no more than 10 yuan ($1.5) per milliliter.

Li also underscored the technology's broad application prospects. These include highly sensitive biosensing chips that can amplify optical signals from viruses, making even "hidden" viruses detectable, as well as photonic chips for VR, AR and other fields, where they help boost transmission efficiency.