Scientists have created a paper battery that is activated by a couple of drops of water

(ORDO NEWS) — A group of Swiss scientists have developed an environmentally friendly and fully biodegradable low-power battery for wearable electronics and sensors.

The battery starts working after applying a couple of drops of water to its surface. A prototype of a pair of such elements powered an electronic clock for more than an hour.

It is expected that such elements will minimize the environmental damage caused by the growing flow of smart electronics.

The prototype of the battery is a strip of plain paper coated with ordinary table salt on its surface. A layer of graphite flakes has been added to one side of the paper – this is done using a specially made paint.

Thus, the battery receives a cathode. An anode in the form of a layer of a mixture of graphite and zinc is applied to the reverse side of the paper.

To start the redox reactions in the battery, which will lead to the generation of electric current, it is enough to put a couple of drops of ordinary water on it.

Scientists have created a paper battery that is activated by a couple of drops of water 2

Water dissolves salt and creates ionic conductivity in the paper layer of the battery. In fact, this is equivalent to pouring electrolyte into a battery.

The zinc oxidation reaction begins in the anode, which releases electrons. If a load is connected to the contacts of the battery, the electrons will run along the wires to the cathode, where a reduction reaction will begin with the capture of oxygen from the air.

This starts a cycle of redox reactions, generating current as long as there is zinc left in the anode to support the reactions, or until the water dries up.

Researchers at the Swiss Federal Laboratory for Materials Science and Technology (EMPA) conducted a proof-of-concept by fabricating two elements in the proposed way and connecting them in series to increase the voltage.

From two drops of water, the element fed the electronic alarm clock for about an hour. A single cell activated 20 seconds after applying water to it and showed a stable voltage of 1.2 V for an hour without load.

When the battery dried out, the scientists added a couple more drops and extended the battery life for another hour or more, although after reactivation, the open-circuit voltage was only 0.5 V.

The developers believe that such batteries can be automatically activated in conditions of high humidity, or it will be possible to create a battery design for normal use after adding water.

Engineers will surely be able to figure out how to keep the battery from drying out ahead of time. It works as long as zinc remains in the anode.

Thus, it is easy to calculate the lifetime of such batteries and print them strictly to maintain power within the specified time limits, which is not possible with alternative technologies, for example, air-metal batteries similar in implementation.

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