Nanoscale printing technique enables two pictures to be printed on the same space

Data storage, digital imaging and anti-counterfeiting could all be revolutionised thanks to the advent of a new miniaturised printing technique dubbed ‘structural colour’.

A team from Glasgow University’s School of Engineering demonstrated the technique by creating a nanoscale image which showed 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.

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

The nanomaterials allow for much higher-resolution prints, which do not fade over time. A typical printed image in a magazine, for example, might consist of around 300 coloured dots per inch of page, or 300 DPI. A page ‘printed’ with structural colour techniques, however, could reach a resolution of 100,000 DPI or more.

The technique allows the ‘printing’ of two entirely different, but exceptionally detailed, full-colour images within the same surface area.

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

“By changing the size and shape of the nanoscale indent, we can create a wide range of different colours at very high resolutions.

“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 1.46Gb per square centimetre, so a single A4 sheet could hold more than 900Gb of data.

Clark added: “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 work was supported by the Royal Academy of Engineering and the Engineering and Physical Sciences Research Council (EPSRC).

In 2013 traditional inkjet printing technology was shown to be able to print cells taken from the eye and could lead to the production of artificial tissue grafts made from a variety of optical cells. 

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