Octopus and cuttlefish can quickly change their skin's color and texture to hide from danger. Scientists want to copy this with man-made materials. Researchers at Stanford have now made a big advance by creating a soft, flexible material that can swell into different textures and colors in seconds. This material makes patterns smaller than a human hair.
The material, described in a paper published in Nature, could help make better camouflage for people or robots, hiding them by matching their surroundings. It might also create screens for wearable devices that change color easily. Another use is in nanophotonics, which is the study of controlling light at very tiny scales for things like better electronics or secure codes.
How the material works
To make these changes, the researchers use electron-beam lithography, a method that shoots a beam of electrons to pattern the material precisely, like in making computer chips. They apply this to a polymer film, a thin plastic layer that swells when it absorbs water. By controlling where the electrons hit, they decide how much each spot swells, creating detailed shapes that appear only when wet. When dry, the material is flat, but water makes the shapes rise up. Adding a solvent like alcohol flattens it again.
For colors, they add thin metal layers to form Fabry-Pérot resonators, devices that pick out certain light wavelengths based on spacing. As the film swells, the colors shift. By mixing water and solvent, they create bright patterns from a plain sheet.
In tests, layering films let them control color and texture separately, almost as well as an octopus. Right now, adjustments are done by hand, but plans include using computer vision, a technology that lets machines see and analyze images, to match backgrounds automatically. Beyond hiding, the material could adjust friction for tiny robots or help in bioengineering by affecting how cells grow on surfaces. This opens many new ideas because no other soft material can change at such small scales.