Which is the highest resolution that can be obtained for colour printing? 
It is determined by the diffraction limit of visible light, and it requires colour elements (pixels) with a pitch of 250 nm. That is, a resolution of ~100,000 dots per inch (d.p.i.). For a comparison, inkjet and laserjet printers have a 10,000 d.p.i. resolution. The highest resolution limit was recently achieved by a research group from the Agency for Science, Technology and Research (A*STAR) in Singapore.

The study, published online in Nature Nanotechnology, illustrates the method that was used to achieve the highest possible resolution limit for printed colour images.

In the used technology, colour information is not encoded in colourants or dyes, but in the dimensions of  metal nanostructures: by changing in the diameters of the elements and the distance between them it is possible to modify the colour of light they reflect.

Each pixel consists of nanospots capped with silver and gold nanodisks. The researchers were able to obtain a full palette of colours that span the visible range by varying the diameter and the spacing of these nanodisks.

The printing method could be used to create microimages or secret messages for security, and to make discs able to store high-density data.