You know bluebirds aren’t really blue, right? Their plumage has no blue pigment; that azure hue comes from nanoscale structural features in the feathers, a phenomenon known as structural color. Chemists and material scientists have been replicating and broadening the effect for a number of years now, creating films and screens in a full range of colors. But one artistic dynamic that has been missing is adjustable brightness, according to Pengcheng Huo of Nanjing University. They use pillars of titanium dioxide to create structures that yield color, similar to other structural color systems. But their pillars also rotate polarized light. So by turning their pillars relative to the orientation of the light polarizer, they can tune the intensity of the light coming back from the “painting” (Optica, 2020, DOI: 10.1364/optica.403092)—in this case, “Girl with a pearl earring” by Dutch master Johannes Vermeer.
Credit: Optical Society of America
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