PARIS: Damnation... your mobile phone, on which your work and social life depend, has become a useless lump of plastic and silicon: the battery is dead.

No problem.

Just reach for the nearest bowl of sugar, flip open the phone, top up the battery with a wee spoonful, give it a little time — and hey presto, you are connected to the world again.

This sci-fi scenario may lie in the not-too-distant future, thanks to a pair of US-based scientists who say they have invented the world’s first efficient “bacterial battery.”

In a Pentagon-backed project, University of Massachusetts researchers Swades Chaudhuri, an Indian, and Derek Lovley, an American, say the battery’s source is an underground bacterium that gobbles up sugar and converts its energy into electricity.

Their prototype device ran flawlessly without refuelling for up to 25 days and is cheap and stable.

The bug in question is Rhodoferax ferriducens, which was found in airless sediment deep below ground at a terrestrial site at Oyster Bay, Virginia, and identified as a promising candidate for oxidising simple sugars.

The two scientists, whose work is published on Sunday in the specialist journal Nature Biotechnology, set up a small two-chambered vessel, with each side containing a graphite electrode and separated by a membrane.

On one side was R. ferriducens swimming in a glucose solution, which it broke down into carbon dioxide (CO2) and electrons.

The electrons were transported to the nearby electrode, called the anode, and driven around an external circuit to the other electrode, the cathode: electrical power.

Microbial fuel cells are not new, but until now they have run into big problems of cost and energy efficiency.

Typically, they yield efficiency of “10 per cent or less,” which makes them big and unwieldy relative to the power they provide, Lovley said.

The best effort has had an efficiency performance of about 50 per cent. But this was only achieved thanks to chemicals called mediators which sneak across the cell’s membranes, pick up the free electrons and ferry them to the anode.—AFP