Borrowing a trick from nature, engineers from the University of California at Berkeley have created an incredibly thin, chameleon-like material that can be made to change color -- on demand -- by simply applying a minute amount of force. This new material-of-many-colors offers intriguing possibilities for an entirely new class of display technologies, color-shifting camouflage, and sensors that can detect otherwise imperceptible defects in buildings, bridges, and aircraft. "This is the first time anybody has made a flexible chameleon-like skin that can change color simply by flexing it," said Dr. Connie J. Chang-Hasnain, a member of the Berkeley team and co-author on a paper published online on March 12, 2015 in Optica, The Optical Society's (OSA) new, high-impact journal. By precisely etching tiny features -- smaller than a wavelength of light -- onto a silicon film one thousand times thinner than a human hair, the researchers were able to select the range of colors the material would reflect, depending on how it was flexed and bent. The colors we typically see in paints, fabrics, and other natural substances occur when white, broad-spectrum light strikes their surfaces. The unique chemical composition of each surface then absorbs various bands, or wavelengths of light. Those that aren't absorbed are reflected back, with shorter wavelengths giving objects a blue hue and longer wavelengths appearing redder and the entire rainbow of possible combinations in between. Changing the color of a surface, such as the leaves on the trees in autumn, requires a change in chemical make-up. Recently, engineers and scientists have been exploring another approach, one that would create designer colors without the use of chemical dyes and pigments.
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