The US technology company last month unveiled a prototype e-paper that looks much more like a sheet of A4 than the offerings of rivals such as Amazon's Kindle and Sony eReader, which resemble paperback books. But Plastic Logic's device is only black and white, not very flexible and its screen updates quite slowly. Liquavista is working on a full-colour flexible screen that would allow newspapers and other publications to provide a much more interactive product that could include video.

The technology is based on a process called electrowetting, which uses electricity to manipulate a thin layer of liquid so that it changes colour. It uses far less power than a traditional LCD and, crucially, the individual cells change fast enough to run video.