Researchers from the Technical University of Denmark demonstrated a new nanotechnology-based printing technique that produces long-lasting color images on plastic at resolutions up to 127,000 dots per inch, many times more detailed than traditional laser printers. The system uses a laser to alter the structure of nanoscale structures on the plastic material. (A nanometer is one-billionth of a meter; a human hair is around 60,000 nanometers in diameter.) The nanoprinting technique could also lead to new kinds of 3D displays or invisible watermarks. From New Scientist:
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.