Glasgow scientists develop new printing method to combat counterfeiting

Scientists at Glasgow University have announced a breaking in high-resolution nanoscale printing' which could be developed for anti-counterfeiting measures in banknotes.

It could also improve data storage and digital imaging as the prints do not fade over time.

Engineers from the University of Glasgow have developed nanoscale plasmonic colour filters that display different colours depending on the orientation of the light which hits it.

This new technique allows the 'printing' of two entirely different, but exceptionally detailed, full-colour images within the same surface areaThe team di

This new technique allows the 'printing' of two entirely different, but exceptionally detailed, full-colour images within the same surface area.

The team, from the university's School of Engineering, have demonstrated their technique with several examples, including a nanoscale image which shows the university's crest when the light reaches it in one orientation, and an image of the university tower when the orientation of the light is reversed.

Biomedical engineering lecturer Dr Alasdair Clark, lead author of the research paper, said: “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.''

Instead of relying on dyes and pigments, as in traditional printing, structural colour uses specially structured nanomaterials to render colours.

These allow for much higher-resolution prints which do not fade over time.

While a typical printed image in a magazine might consist of around 300 coloured dots per inch of page, or 300 DPI, a page 'printed' with structural colour techniques could reach a resolution of 100,000 DPI or more.

Dr Clark said: “There are a lot of potential applications for our plasmonic colour technology, which we're really excited about.

“It's ideal for long-term data archival due to its ultra-high resolution, and because the colours won't fade even when exposed long-term to the harshest sunlight. We've worked out that we could store 1.46 Gb per square centimetre, so a single A4 sheet could hold more than 900 Gb of data.

“Secondly, the process to produce the plasmonic colours is difficult to replicate without access to dedicated facilities, so it could be ideal for creating a new kind of anti-counterfeiting material for banknotes.

“Lastly, it offers the possibility of developing new types of colour filters for digital photography.''

The paper, titled Plasmonic color filters as dual-state nano-pixels for high density micro-image encoding, is published in Advanced Functional Materials.

The work was supported by the Royal Academy of Engineering and the Engineering and Physical Sciences Research Council (EPSRC)