Chameleons change their color based on mood, but humans could benefit from multiple “skin” hues as well. Now, researchers at UC Berkeley have created exactly that – an ultra-thin film that changes color on demand. Rather than rely on dyes or pigment, the thin film changes color by manipulating light itself, which is in fact very similar to how chameleons themselves change their appearance.
“We were fascinated by the chameleon’s ability to change colors, and the process of mimicking their skin has been exciting,” said Connie Chang-Hasnain, professor of electrical engineering and computer sciences. “The coolest thing is that you can hold the sample film and stretch it to see the colorful effect.”
The process starts with a layer of silicon film about 1,000 times thinner than a human hair. From there, the researchers then etched a series of ridges into the film, with the distance between each ridge being less than the wavelength of light. The resulting product reflects 83% of the light that hits it, and it can change colors from green to a brilliant orange depending on the spacing between the ridges. All it takes is a simple twist, bend or pull on the film.
This is, coincidentally, similar to how chameleons change their appearance by manipulating light. Using a layer of cells called iridophores just below the surface of their skin, chameleons can alter the salt balance of these iridophores, making them swell or shrink and effectively altering the distance between reflective guanine crystallites. Just like with UC Berkeley’s reflective film, when the distance between reflective surfaces changes, so too does the color.
The applications for such a technology a myriad. Once improved, it could act as a kind of adaptive camouflage for military weapons and vehicles, or be adapted to create ultra-thin display devices. Perhaps most creatively, the film could act as an early warning system for infrastructure objects, like roads and bridges. If applied tightly to stressed areas so as to be transparent, any changes in color would indicate structural shifts.