A method for printing colours at the highest possible resolution is reported in a paper published online this week in Nature Nanotechnology. The resolution of about 100,000 dots per inch could be useful for high-resolution printing for security purposes or for high-density optical data storage.

Joel Yang and co-workers demonstrate colours that arise from the light scattered back from silver nanodisks that are raised above a silver plane acting as a back-reflector. The diameter of the nanodisks and their separation encode for the reflected colour. An individual colour pixel shown in this work is made of a two-by-two array of these nanodisks. As a striking example for their technique, the team recreated the details and shades of the famous Lena test image.

The resolution achieved by the team surpasses that of earlier attempts by around 10 times thanks to directional back-reflection, as opposed to random scattering, exhibited by the disk-back-reflector nanoarchitecture, which supports plasmon resonances from silver.