Carving nanostructures with a laser creates long-lasting colors.
Researchers developed the new printing technique as an alternative to ink-based printing, in which colors fade with time. Aside from eternally vibrant art, the technique could lead to new types of color displays or improve security labels, the scientists report in the May 5 Science Advances.
Anders Kristensen of Technical University of Denmark in Kongens Lyngby and colleagues designed the laser printing technique so that it requires only three materials: plastic, germanium and a protective coating. In traditional ink-based printing, paper acts as the base; in the new method, plastic provides the foundation. The surface of the plastic is shaped so that it has lots of tiny pillars, one roughly every 200 nanometers. A thin film of the element germanium is then spread over the plastic. Heat from a laser melts the germanium on each pillar, morphing its shape and thickness. As a result, it reflects a specific color. The coating protects the shapes of the newly carved nanostructures.
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