DÜBENDORF, Switzerland — A new “just-add-water” disposable paper battery could power small-scale electronics such as smart labels for tracking parcels and medical diagnostic devices.
Since the new invention is made of paper and contains zinc, both of which are biodegradable, scientists say it could help reduce the environmental impact of battery waste. Devised by Dr. Gustav Nyström and colleagues at the Swiss Federal Laboratories for Materials Science and Technology, the battery is made of at least one cell that measures one square centimeter in size.
Three ink markings cover a rectangular piece of paper, which contains sodium chloride salt, while one end of the paper is covered in wax. On one side of the paper is the first ink marking, which contains graphite flakes and acts as the positive end of the battery. On the other side is another ink marking containing zinc powder, which acts as the negative end of the battery.
A third ink marking is printed on both sides, which contains graphite flakes and carbon black ink, and this connects the positive and negative ends of the battery to two wires which sit at the wax-dipped end of the paper.
When scientists added a few drops of water, the salts in the paper dissolved, releasing charged ions. These ions activate the battery by dispersing through the paper and causing the zinc at the negative end to release electrons.
The electrons move from there to the positive end via the graphite, carbon black ink, and the wires — where they become oxygen and disperse into the air. All these reactions create an electrical current that can power a device.
Replacing the AA battery?
Presenting their work in the journal Scientific Reports, the researchers demonstrated their battery’s abilities by combining two cells into one battery and using it to power an alarm clock with a digital display.
Two drops of water made the battery activate after 20 seconds. When not powering an energy-draining device, the battery reached a voltage of 1.2 volts. In comparison, the voltage of a standard AA battery is 1.5 volts.
The battery’s performance dropped considerably after an hour because the paper dried out. However, when researchers added two more water drops, it kept a stable voltage of 0.5 volts for an extra hour and more.
Dr. Nyström says the biodegradability of paper and zinc means their battery could minimize the environmental impact of low-power electronics. The research team adds that they could further enhance paper batteries by reducing the amount of zinc in the ink, which would also mean the electricity the battery generates could be more precisely controlled.
South West News Service writer Danny Halpin contributed to this report.