Nanodisks of gold and silver can create colour prints with a resolution of 100,000 dpi

Bright colours and fine tonal variations have been achieved without a dye or paint in sight. Joel Wang’s group at A*STAR in Singapore used nanopillars to print an image at 100,000 dots per inch.

Just as stained glass uses suspensions of gold and silver nanoparticles to achieve different colours, by varying the size and spacing between the nanoposts Wang was able to create a full palette. And as proof, he printed a 50 x 50µm Lena image (pictured), which is often used as a printing standard.

The image is made by etching nanoposts, of defined sizes and spacing, out of silicon coated with a reflective gold-silver alloy. The posts are then topped with more of the gold-silver alloy to create the colour by particle resonance.

Because the colour is structural in origin the colour shouldn’t fade over time, unlike dyes, making the technique useful as a ‘watermark’ or for long term information storage.