Paper power

Printable lightweight cellulose batteries on the horizon

Batteries have come a long way – and could have a lot further to go. Our lifestyles demand ever more, smaller, lighter portable power – without the pollution penalty of toxic metals. Now scientists at the Rensselaer Polytechnic Institute in the US have developed a thin flexible battery not much bigger than a postage stamp which can be rolled, cut, stacked and even printed in exactly the same way as paper.

Like ordinary paper, it’s made mainly of plant-derived cellulose, but infused with tiny aligned carbon nanotubes which act as electrodes and allow it to conduct electricity. Since its components are all integrated into a single system, there is less energy lost in the transfer between components, making it more efficient than standard batteries.

The paper battery contains ionic liquid electrolytes to activate it, but it could also run on the naturally occurring electrolytes in human sweat, blood or urine – so it lends itself readily to powering devices implanted in the body, such as heart pacemakers. Other uses put forward by the team include handheld electronic gadgets and even, one day, cars.

“This technology is just right for the current energy market, especially when looking for greener, smaller and lighter power source devices,” said Victor Pushparaj, the project’s lead researcher. His team envisages manufacturing it using a roll-to-roll system, the same way newspapers are produced, but has yet to develop an inexpensive mass production method. – Anna Blackaby

19 September 2007