Researchers at ITMO University in Russia have created a “laser paintbrush” capable of creating localized color on a metallic canvas, using their method to create miniaturized replicas of various works of art—including Vincent van Gogh’s The Starry Night. Their technique even makes it possible to change or erase or rewrite the colors several times. They described their work in a new paper published in the journal Optica.
Traditional paints get their colors from various pigments (often derived from minerals), but there are many examples of structural color in nature, like the bright colors in butterfly wings. As we’ve reported previously, those colors don’t come from pigment molecules but from how the wings are structured. The scales of chitin (a polysaccharide common to insects) are arranged like roof tiles. Essentially, they form a diffraction grating, except these naturally occurring photonic crystals only produce certain colors, or wavelengths, of light, while a diffraction grating will produce the entire spectrum, much like a prism. Alter the structure by changing the size of the tiles, and the crystals become sensitive to a different wavelength. And the perception of color doesn’t depend on the viewing angle.
Manmade “nanopillars” can also be used to generate structural colors, for instance, by illuminating nanopillar arrays with white light to produce specific colors (red, blue, and green light), simply by varying the sizes (widths) of the nanopillars. In fact, last year, scientists at the National Institute of Science and Technology (NIST) used millions of nanopillars in an array to control both the color and intensity of incident light, projecting a faithful reproduction of Johannes Vermeer’s Girl With a Pearl Earring as proof of concept.