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#Engineers create chameleon-like artificial'skin'that shifts color on demand Abstract: 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 Connie J. Chang-Hasnain, a member of the Berkeley team and co-author on a paper published today 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. A Material that's a Horse of a Different Colorthe 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. Rather than controlling the chemical composition of a material it's possible to control the surface features on the tiniest of scales so they interact and reflect particular wavelengths of light. This type of"structural color"is much less common in nature, but is used by some butterflies and beetles to create a particularly iridescent display of color. Controlling light with structures rather than traditional optics is not new. In astronomy, for example, evenly spaced slits known as diffraction gratings are used routinely to direct light and spread it into its component colors. Efforts to control color with this technique, however, have proved impractical because the optical losses are simply too great. The authors of the Optica paper applied a similar principle though with a radically different design, to achieve the color control they were looking for. In place of slits cut into a film they instead etched rows of ridges onto a single, thin layer of silicon. Rather than spreading the light into a complete rainbow, however, these ridges--or bars--reflect a very specific wavelength of light. By"tuning"the spaces between the bars, it's possible to select the specific color to be reflected. Unlike the slits in a diffraction grating, however, the silicon bars were extremely efficient and readily reflected the frequency of light they were tuned to. Flexibility Is the Key to Controlsince the spacing or period, of the bars is the key to controlling the color they reflect, the researchers realized it would be possible to subtly shift the period --and therefore the color--by flexing or bending the material.""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. Earlier efforts to develop a flexible, color shifting surface fell short on a number of fronts. Metallic surfaces, which are easy to etch, were inefficient, reflecting only a portion of the light they received. Other surfaces were too thick, limiting their applications, or too rigid, preventing them from being flexed with sufficient control. The Berkeley researchers were able to overcome both these hurdles by forming their grating bars using a semiconductor layer of silicon approximately 120 nanometers thick. Its flexibility was imparted by embedding the silicon bars into a flexible layer of silicone. As the silicone was bent or flexed, the period of the grating spacings responded in kind. The semiconductor material also allowed the team to create a skin that was incredibly thin, perfectly flat, and easy to manufacture with the desired surface properties. This produces materials that reflect precise and very pure colors and that are highly efficient, reflecting up to 83 percent of the incoming light. Their initial design, subjected to a change in period of a mere 25 nanometers, created brilliant colors that could be shifted from green to yellow, orange, and red-across a 39-nanometer range of wavelengths. Future designs, the researchers believe, could cover a wider range of colors and reflect light with even greater efficiency. Chameleon Skin with Multiple Applicationsfor this demonstration, the researchers created a one-centimeter square layer of color-shifting silicon. Future developments would be needed to create a material large enough for commercial applications.""The next step is to make this larger-scale and there are facilities already that could do said so Chang-Hasnain.""At that point, we hope to be able to find applications in entertainment, security, and monitoring.""For consumers, this chameleon material could be used in a new class of display technologies, adding brilliant color presentations to outdoor entertainment venues. It also may be possible to create an active camouflage on the exterior of vehicles that would change color to better match the surrounding environment. More day-to-day applications could include sensors that would change color to indicate that structural fatigue was stressing critical components on bridges, buildings, or the wings of airplanes.""This is the first time anyone has achieved such a broad range of color on a one-layer, thin and flexible surface,"concluded Change-Hasnain.""I think it's extremely cool."#"##About The Optical Societyfounded in 1916, The Optical Society (OSA) is the leading professional organization for scientists, engineers, students and entrepreneurs who fuel discoveries, shape real-life applications and accelerate achievements in the science of light. Through world-renowned publications, meetings and membership initiatives, OSA provides quality research, inspired interactions and dedicated resources for its extensive global network of optics and photonics experts. OSA is a founding partner of the National Photonics Initiative and the 2015 International Year of Light. For more information, visit www. osa. org. About Opticaoptica is an open-access, online-only journal dedicated to the rapid dissemination of high-impact peer-reviewed research across the entire spectrum of optics and photonics. Published monthly by The Optical Society (OSA Optica provides a forum for pioneering research to be accessed swiftly by the international community, whether that research is theoretical or experimental, fundamental or applied. Optica maintains a distinguished editorial board of more than 20 associate editors from around the world and is overseen by Editor-In-chief Alex Gaeta of Cornell University. For more information, visit optica. osa. org. For more information, please click herecontacts: Jack Hanleywriteemail('ecius. net','optica';'202-296-2002copyright#The Optical Societyissuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content. Bookmark: Paper: L. Zhu, J. Kapraun, J. Ferrara, and C. J. Chang-Hasnain,"Flexible photonic metastructures for tunable coloration,"Optica, 2, 3, 255-258 (2015): News and information Super-resolution microscopes reveal the link between genome packaging and cell pluripotency: A study using super-resolution microscopy reveals that our genome is packaged not regularly and links these packaging differences to stem cell state March 12th, 2015sweet nanoparticles target stroke March 12th, 2015turmeric Extract Applied in Production of Antibacterial Nanodrugs March 12th, 2015discovery demystifies origin of life phenomenon: University of Akron polymer scientist finds that certain amino acids and sugars were meant simply to be in life March 11th, 2015thin films Researchers synthesize new thin-film material for use in fuel cells: Article in the journal APL Materials shows how to grow Bi2pt2o7 pyrochlore, potentially a more effective cathode for future fuel cells March 10th, 2015graphene meets heat waves March 9th, 2015ciqus researchers obtain high-quality perovskites over large areas by a chemical method March 4th, 2015researchers enable solar cells to use more sunlight February 25th, 2015display technology/LEDS/SS Lighting/OLEDS Breakthrough in OLED technology March 2nd, 2015new nanowire structure absorbs light efficiently: Dual-type nanowire arrays can be used in applications such as LEDS and solar cells February 25th, 2015qd Vision Named Edison Award Finalist for Innovative Color IQ Quantum dot Technology February 23rd, 2015sensors The Universitat Politcnica de Valncia is coordinating a European project to develop a device for the quick and early diagnosis of cancer March 7th, 2015experiment and theory unite at last in debate over microbial nanowires: New model and experiments settle debate over metallic-like conductivity of microbial nanowires in bacterium March 4th, 2015pens filled with high-tech inks for do-it-yourself sensors March 3rd, 2015researchers build atomically thin gas and chemical sensors: Sensors made of molybdenum disulfide are small, thin and have a high level of selectivity when detecting gases and chemicals February 19th, 2015discoveries Super-resolution microscopes reveal the link between genome packaging and cell pluripotency: A study using super-resolution microscopy reveals that our genome is packaged not regularly and links these packaging differences to stem cell state March 12th, 2015sweet nanoparticles target stroke March 12th, 2015turmeric Extract Applied in Production of Antibacterial Nanodrugs March 12th, 2015is US immigration policy'STEMMING'innovation? 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