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Researchers have developed artificial 'chameleon skin' that changes color when exposed to light and could be used in applications such as active camouflage and large-scale dynamic displays.
The material, developed by researchers from the University of Cambridge, is made of tiny particles of gold coated in a polymer shell, and then squeezed into microdroplets of water in oil. When exposed to heat or light, the particles stick together, changing the color of the material. The results are reported in the journal Advanced Optical Materials.
Nature - Animals - Chameleons - Cuttlefish - Color
In nature, animals such as chameleons and cuttlefish are able to change color thanks to chromatophores: skin cells with contractile fibers that move pigments around. The pigments are spread out to show their color, or squeezed together to make the cell clear.
The artificial chromatophores developed by the Cambridge researchers are built on the same principle, but instead of contractile fibers, their color-changing abilities rely on light-powered nano-mechanisms, and the 'cells' are microscopic drops of water.
Material - Nanoparticles - Amounts - Energy - Fraction
When the material is heated above 32C, the nanoparticles store large amounts of elastic energy in a fraction of a second, as the polymer coatings expel all the water and collapse. This has the effect of forcing the nanoparticles to bind together into tight clusters. When the material is cooled, the polymers take on water and expand, and the gold nanoparticles are strongly and quickly pushed apart, like a spring.
"Loading the nanoparticles into the microdroplets allows us to control the shape and size...
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