A design for a thin, electronic display that operates using ambient light and promises brightness and colour that mimics printed ink on paper is reported online this week in Nature Photonics. With a response speed on the millisecond timescale, display of video images should be possible.

The prototype displays made by Jason Heikenfeld and colleagues use electrically controllable forces to direct the spread of water-based coloured inks over the surface of polymer pixels that are coated with high-reflectivity aluminium.

With no electrical voltage applied, the ink remains in a small well in the centre of the pixel and the ambient light is strongly reflected by the aluminium. When a voltage is applied, the ink is pulled out of the well to cover the surface of the pixel, providing a strong vivid colour.

The research is still at an early stage and at present demonstrations with only one colour of ink have been reported. The future challenges are to create a full-colour version and integrate the design with necessary technology to allow for many shades of colour too.