So everyone wanted to be a chameleon at least once in their life. How cool would it be if you could change color on demand? Imagine wearing clothes that could change colors. Well, what if you could wear such skin? Skin that could change color on demand? Awesome right?
A team of engineers in the University of California, Berkeley have succeeded in creating an artificial chameleon like skin that could change color by simply flexing it. This was achieved by etching intricate features- features smaller than the wavelength of light – on a very thin silicon film more than a thousand times thinner than a hair strand. This allows the skin to change colors by applying just a tiny amount of force. This new color changing skin offers interesting possibilities that would widen the realm of display technology, color shifting camouflage, and sensors that can detect otherwise imperceptible faults in buildings, bridges and aircrafts.
Generally, the colors seen in paints, fabrics and other materials are due to the chemical composition of them that results in the absorption of a definite set of wavelengths of light and reflecting a particular set. The change in color of leaves in autumn, for that reason, is the result of the change in the chemical make- up.
Rather than a chemical approach to the subject of changing colors, engineers and scientists have recently been working on another approach – an optical approach; which could help change colors without the aid of chemical pigments and dyes. Rather than controlling the chemical composition of a material, it is possible to control the surface features of the material on the teeniest scale so they interact and reflect particular wavelengths of light. This approach is borrowed by the structural display of some butterflies and beetles that make use of such principle to showcase a particularly iridescent display of color.
The principle behind the working of this color changing skin is similar to diffraction, but not quite it. Astronomers make use of diffraction gratings to direct light and divide it into its components. This diffraction has been tried but proved impractical due to the immense optical losses.
Instead, engineers used a similar approach, though with a different design, to achieve the color control they have been looking for. In place of slits cut on to a thin silicon film, they etched a series of ridges (or bars) onto the surface of the film that could reflect a very specific wavelength of light. By tuning the space between the bars, it is possible to select the color to be reflected.
Since the spacing, or period, of the bars is the key to specifically select a wavelength of light, it would be possible to subtly shift the period, and hence the color, by flexing or bending the material. The flexibility of the skin was achieved by incorporating the silicon bars onto a thin layer of silicone. The silicon bars are approximately 120 nanometers thick. As the silicone was bent or flexed, the period of the gratings spacing responded in kind.
The semiconductor material also allowed to create a skin that was incredibly thin, perfectly flat and easy to manufacture.
This chameleon-like color changing skin could be used in innovative display technologies, adding brilliant color texture to outdoor venues. Applications also include sensors that could change color to warn about the structural fatigues in the critical components on bridges, buildings, aircraft wings etc.
Are you excited to witness a color changing skin’s applications? Tell us in comments!
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