Mixing dyes with DNA could be the solution for bright, robust electronic displays and digital paper.

Japanese chemists have discovered that DNA strands make useful hosts for electrochemically-responsive dyes called viologens. These electrochromic molecules, which change colour from pale yellow to deep blue when triggered by a current, are promising candidates for display devices. However, bright displays require that the dye is used in high concentration, conditions under which viologens typically dimerise, and eventually stop working.

Hiroyuki Ohno and colleagues at the Tokyo University of Agriculture and Technology have successfully overcome viologen dimerisation by trapping the dye within grooves in the DNA double helix. Ohno used a polymerised ionic liquid to act as the electrolyte. This mixture, held between two transparent glass electrodes, could be repeatedly cycled between coloured and bleached states without deterioration, said Ohno.

'It's not well known that DNA is a very cheap biopolymer, and a large amount of DNA is awaiting application,' said Ohno. And the technique isn't limited to viologens, Ohno added, 'DNA is expected to be a useful matrix for most dye molecules,' and 'may open new possibilities in display devices,' he said.

Roger Mortimer, who researches electrochromism at Loughborough University, UK, agreed that the DNA host was an effective mechanism to stop dimerisation. 'A huge amount of electrochromics research is done on single electrodes, but in this case they have made a working device,' Mortimer added.

James Mitchell Crow