Engineers at the University California at Berkeley have mimicked a trick used by insects to create an ultra-thin material that can change color on demand by applying a small amount of pressure.

The material offers a wide variety of both practical and decorative applications including camouflage, display technologies and structural safety products.

“This is the first time anybody has made a flexible chameleon-like skin that can change color simply by flexing it,” said Connie J. Chang-Hasnain, a member of the Berkeley team and co-author on a paper published today in Optica, in a statement.

The researchers etched features, smaller than a light wavelength onto silicon film so thin that it would take a thousand of them to equal the width of a human hair. With the fine etching, the material reflects different wavelengths of light depending on how it is bent.

Normally, objets reflect colors based on the chemical composition of their surface. When struck by broad spectrum light, certain colors are absorbed and others are reflected. The colors that are reflected are the ones we perceive as red, blue, green or anything in between. Changing the color of an object requires a change in the chemical makeup of its surface.

The approach taken by the Berkeley engineers was to control the surface features to reflect certain wavelengths rather than changing the chemical make up. It is a trick used by certain species of butterflies and beetles in nature.

To achieve the task, rows of ridges were etched onto a thin layer of silicon. Instead of spreading the light into a rainbow, these ridges reflect specific wavelengths of light. By bending or flexing the silicon it is possible to achieve a different reflective surface and change the perceived color.

“If you have a surface with very precise structures, spaced so they can interact with a specific wavelength of light, you can change its properties and how it interacts with light by changing its dimensions,” said Chang-Hasnain.

This approach is not very different from the one chameleons employ to change color. In a paper published in Nature Communications this month researchers showed that chameleons change their color by rearranging tiny crystals in the surface layers of the skin.

The Berkeley researchers end product was an incredibly thin, flat material that is easy to manufacture. The slightest shift in the material chan change the color from green to yellow, orange or red. The engineers believe that further development can lead to an even wider range of colors.

The current prototype of the material is only one centimeter square so before it can be put to practical use, a larger scale production method needs to be created.

“The next step is to make this larger-scale and there are facilities already that could do so. At that point, we hope to be able to find applications in entertainment, security, and monitoring,” said Chang-Hasnain.

The team sees a variety of applications including “brilliant color presentations to outdoor entertainment venues” as well as camouflage for vehicles and always-on sensors that could warn of structural fatigue in buildings, bridges, airplanes or other structures and vehicles.