A DISPOSABLE PAPER BATTERY THAT RUNS ON WATER

A few clever inks can make paper electric.

A team of Swiss researchers has made a disposable battery out of paper.

The paper battery, described in Scientific Reports, is printed with a couple of inks that perform the function of the battery. It’s inert until you add a few drops of water, which allows ions to move between the inks and electricity to flow.

It’s powerful enough to run a small LCD alarm clock, and it can run for an hour – two hours if it’s dampened again. The battery is printed on a few square centimetres of paper. It uses two different inks as its anode and cathode: the anode ink is mostly zinc powder, while much of the cathode ink is graphite flakes. Both inks also have shellac, ethanol and polyethylene glycol in varying amounts to make them printable.

The anode and cathode inks are connected by a bridge of sodium chloride – table salt – in the middle. When dampened, the salt ions allow the anode and cathode inks to exchange positively and negatively charged particles, letting electrons flow through the wires.