Bio Focus: Turkey skin inspires biomimetic sensor
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Resonant scattering from silver nanoparticles enhances transparent display performance
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mbedding silver nanoparticles in a thin polymer sheet can produce transparent displays based on narrowband resonance scattering phenomena, according to research reported in the January 21 issue of Nature Communications (DOI: 10.1038/ncomms4152) by scientists at the Massachusetts Institute of Technology (MIT) and the US Army Edgewood Chemical Biological Center. The frequency-selective properties of these displays, which can be tuned to scatter light of a desired, single wavelength, and their wide viewing angle, make them attractive possible alternatives to currently available transparent displays. Eventually, they might be manufactured inexpensively on a large scale using roll-to-roll polymer processing, which would give them a cost advantage over other display types. As an example, the head-up display in aircraft that projects flight data on the cockpit window for easy viewing by the pilot works by specular reflection of the images off the glass. This reflection limits the angle of viewing and the images can be seen only from the pilot's seat; they are not visible to someone standing behind the pilot or off to one side. In contrast, the scattering of an image from the new
Bio Focus Turkey skin inspires biomimetic sensor
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n the United States, turkeys usually only make the press around Thanksgiving, when they play the star role in this annual feast. In Korea and Japan, said Seung-Wuk Lee of the University of California– Berkeley, “they call the turkey the seven-faced bird because it can show seven different colors on its face.” For example, when a turkey is excited, the red skin on its face changes to white or blue. Now, the color-changing properties of their skin are inspiring biomimetic sensors that can de-
silver-nanoparticle-embedded plastic film can be seen over a wide range of viewing angles. “This makes it useful for viewing by multiple audience members,” said Chia Wei Hsu of MIT and Harvard University, the lead author of the article. The proof-of-concept display developed by Hsu and his colleagues is also more transparent to ambient light than most other types of transparent displays because of its frequency selectivity. By changing the diameter and volume fraction of the silver nanoparticles, it is possible to tune the frequency of light that is scattered. Most head-up displays are not frequency-selective, so basically all of the light is either reflected or transmitted, Hsu said; to reflect more light, it has to be made less transparent. “In our case we can make the display scatter this one particular color but keep the transparency at other colors,” he said, “so we won’t have to decrease the transparency as much.” The research team’s display was measured at 60% transparency in the visible range, compared to 20–40% for liquid-crystal displays or organic lightemitting diodes. The research team chose silver nanoparticles for this initial trial because silver provided the best performance among the materials they ha
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