Hamburg  - A team of German scientists has invented the world's first printable batteries, wafer-thin and environmentally friendly batteries which can be produced in large quantities for a fraction of what it takes to produce conventional batteries.

The new battery is also different in other ways from conventional batteries. The printable version weighs less than one gram on the scales, is not even one millimetre thick and can therefore be integrated into bank cash cards, for example.

The battery contains no mercury and is in this respect environmentally friendly. Its voltage is 1.5 V, which lies within the normal range.

By placing several batteries in a row, voltages of 3 V, 4.5 V and 6 V can also be achieved.

The new battery was developed by a research team led by Dr Reinhard Baumann of the Fraunhofer Research Institution for Electronic Nano Systems ENAS in Chemnitz, Germany.

"Our goal is to be able to mass produce the batteries at a price of single digit cent range each," states Dr Andreas Willert, group manager at ENAS.

The batteries are printed using a silk-screen printing method similar to that used for t-shirts and signs. A kind of rubber lip presses the printing paste through a screen onto the substrate. A template covers the areas that are not to be printed on.

Through this process it is possible to apply comparatively large quantities of printing paste, and the individual layers are slightly thicker than a hair.

Therefore, the battery is suitable for applications which have a limited life span or a limited power requirement, for instance greeting cards.

The researchers have already produced the batteries on a laboratory scale. At the end of this year, the first products could possibly be finished. (dpa)