The Singapore-based team, who describe their work in a paper in Nature Nanotechnology, created pixels using tiny nanoscale posts, with silver and gold nanodiscs on top. The distance between these structures, and their diameter, sets the colour of light that they reflect.
As proof of concept, the researchers, based at Singpore’s Agency for Science, Technology and Research, printed a 50 x 50 micrometer image of Lena Söderberg, a Swedish model from a 1972 issue of Playboy magazine, often used in image processing experiments.
They used electro-beam lithography to cover a silicon wafer with pillars made from an insulating material, then deposited the nanodiscs on top and coated the surface of the wafer with metal to reflect the coloured light and make the image brighter. The resulting image came in at an impressive 100,000 DPI resolution.
That’s right up at the maximum possible resolution that can be achieved. Even under the best microscope, a limit can be reached due to the wavelength of visible light. If two objects are too close together, light reflecting off them will diffract and they’ll blur together. In the case of visible light, in the centre of the colour spectrum, that distance is 250 nanometers — exactly the distance between the pixels in the created image.
The other benefit of using nanostructures to create colour is that they’ll never fade. So long as the pillars don’t corrode and change shape, the image won’t change over time.
Read more at Wired Science
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