Ahem. No sniggering at the back. This is a serious subject.

A urine powered battery the size of a credit card has been invented by Singapore researchers.

A drop of urine generates 1.5 volts, the equivalent of one AA battery, says Dr Ki Bang Lee of the Institute of Bioengineering and Nanotechnology. He says the technology could provide a disposable power source for electronic diagnostic devices that test urine and other body fluids for diseases like diabetes.

These currently need lithium batteries or external power sources. But with this system, the body fluid being tested could power the unit itself.

Lee, who reports the new battery in the latest Journal of Micromechanics and Microengineering, says a smaller version could potentially power mobile phones in emergencies.

The battery is made of a layer of filter paper steeped in copper chloride sandwiched between strips of magnesium and copper, then laminated in plastic.

It’s activated when a drop of urine is placed on the battery. The urine soaks through the paper providing the necessary conditions to generate electricity. The magnesium acts as the battery’s anode, shedding its electrons, while the copper chloride acts as the cathode, gathering them up.

This electron flow delivers power greater than 1.5 milliwatts, the researchers say.

Coming soon: electricity generation from hot air emitted by University Committees.

Thanks to Quentin for the link.