The Battery of the Future: Paper Made, in Whatever Shape You Want and Fueled by Sweat, Urine and Blood!

A battery is in many cases that which impedes the size of many gadgets and implantable medical devices from dwindling. That's why the battery of the future is lightweight, ultra thin and completely flexible.

The battery of the future has just been designed by a team at Rensselaer Polytechnic Institute. The new model is completely integrated and can be printed like paper, rolled, twisted, folded, or cut into any desired shape without losing effectiveness or integrity. The new batteries can be even stacked to increase the total power output.

Over 90 % of the device is made up of cellulose (the material paper or cotton are made of), being thus ecological and the rest is made of carbon nanotubes (giving the battery the black color).

Moreover, the device works as both a high-energy battery and a high-power supercapacitor, which are normally separate components in the electrical systems and is functional in a range of temperatures up to 300� F (150 �C) and down to -100� F (-73 �C). It can also make use of human blood, sweat or urine to increase power.

"It's essentially a regular piece of paper, but it's made in a very intelligent way," said co-author Robert Linhardt, the Ann and John H. Broadbent Senior Constellation Professor of Biocatalysis and Metabolic Engineering at Rensselaer.

The nanotubes function like electrodes, allowing for the electric conductivity. The device delivers the long, steady power output like a lithium-ion battery, but also bursts of high energy like a supercapacitor.

"We're not putting pieces together - it's a single, integrated device. The components are molecularly attached to each other: the carbon nanotube print is embedded in the paper, and the electrolyte is soaked into the paper. The end result is a device that looks, feels, and weighs the same as paper." said Linhardt.

A liquid salt acts as the battery's electrolyte. The ionic liquid has no water, thus there's nothing in the batteries to freeze or evaporate, explaining the devices' resistance to extreme temperatures. The battery could be used not only in small handheld electronics, but also in automobiles, aircraft and even boats. As it can be shaped on the desired forms, like a car door, it could enable crucial engineering innovations.

As cellulose is highly biocompatible, the device would be the choice for power supplies for implantable devices. The paper batteries would not further require adding any electrolytes, as it can use the naturally occurring electrolytes in human sweat, blood and urine.

The efficiency of the device could be further improved and different manufacturing techniques could be used, like a roll-to-roll system similar to the printing of the newspapers. There is also a cost obstacle: the carbon nanotubes, which for the moment block a mass production.