A team of German scientists claim to have invented an ultra-thin battery that weighs less than a gram, measures less than a mm in thickness and can be printed out.

They can provide 1.5V each, so in series they'll put out up to 6V. What's more, the team reckons the batteries could be ready for commercial-scale duplication by the end of the year.

"They contain no mercury, so aren't particularly environmentally unfriendly. They are printed using a silk-screen method just like that used for t-shirts and signs".

"A rubber lip presses the printing paste through a screen onto the substrate, with a template covering the areas that are not to be printed on. The individual layers are slightly thicker than a hair".

So where's the downside? Well, the scientists say that they won't hold much charge for very long, so they won't be powering your mobile phone just yet. They could, however, be perfect for musical greetings cards and other similar applications.