Scientists at the Swiss Federal Laboratories for Materials Science and Technology (EMPA) have created a disposable battery made of paper that is activated by water.

A strip of paper, two electrochemical cells at the end of the paper separated by a water barrier that joins the letters "m" and "p", as shown in the image below. Each cell is 1 square centimeter and consists of three printed inks, graphite, zinc powder and carbon black. Salt was placed all over the paper and one end was dipped in wax.

As the authors quoted by the Green Svers portal explain, "an ink with graphite flakes, which acts as the positive end of the battery (the cathode), is printed on one flat side of the paper, while an ink with zinc powder, which acts as the negative end of the battery (the anode) is printed on the back of the paper. Another ink with graphite flakes and carbon black is printed on both sides of the paper, on top of the other two inks." When water is added to the paper, all these materials generate an electric current that runs the device.

In the course of study, the performance of a one-cell battery showed that after adding two drops of water, the battery was activated within 20 seconds, and that when it was not connected to a device that consumed the power, it reached a stable voltage of 1.2 volts.

The innovative battery could be used to power low-power electronic equipment, such as environmental sensors, smart labels, and medical diagnostic devices.

"What's special about our new battery is that, unlike many air metal batteries that use a sheet of metal that is gradually consumed as the battery depletes, our design allows you to add only the amount of zinc to the ink that is actually needed for the application," explains Gustav Nyström, the author who coordinated the research, stressing that this alternative makes it possible to minimize the environmental impact of disposable electronic equipment.