The scientists from the University of Glasgow, Scotland have discovered a new form of high-resolution printing that can be used as an anti-counterfeiting measure in banknotes in addition to data storage and digital imaging.
The team has developed nanoscale plasmonic colour filters that will display different colours depending on the orientation of the light that touches it.
This technique was demonstrated through various examples like when the light reached one orientation, the nanoscale image showed university’s crest and when the orientation of the light was reversed, an image of the university tower could be viewed.
According to Dr. Alasdair Clark, a biomedical engineering lecturer and a lead author of the research paper, “We’ve discovered that if we make colour pixels from tiny cross-shaped indents on a strip of aluminium film, the colour they display becomes polarisation-dependent, allowing us to encode two colours into a single pixel, and then select which colour is displayed by shining different polarisations of light at the surface. By changing the size and shape of the nanoscale indent, we can create a wide range of different colours at very high resolutions.”
The scientists further added that the Plasmonic colour filtering has provided a new range of techniques for “printing” images at resolutions beyond the diffraction-limit, unlike images obtained when traditional, dye-based filtering methods were used.
Explaining the difference, one of the engineers said that a page printed with structural colour techniques could reach a resolution of 100,000 DPI and even more, in comparison to a typical printed image in a magazine which consists around 300 coloured dots per inch of page or 300 DPI.
He further explained that with a PPI [pixels per inch] value exceeding 100,000, each will be able to encode two colour states, this technology may prove useful for high-resolution printing applications and counterfeit-prevention measures.