Scientists have developed a water-activated, disposable, paper battery, according to a proof-of-concept study published in Scientific Reports. The developers believe that their invention could be used to power a variety of low-power, single-use electronics, such as smart packaging, environmental sensors and medical diagnostic devices, thereby reducing their environmental impact.

The single-cell battery consists of one square centimeter of paper treated with salts. One side is printed with ink containing graphite flakes, which serves as the positive terminal, and the other side is printed with ink containing zinc powder to create the negative terminal. Another layer of ink containing graphite flakes and carbon black is applied over that, linking the battery’s positive and negative ends to two wires secured by wax.

When a few drops of water are added to the paper, the salts dissolve, releasing charged ions that spread across the paper to activate the battery. In tests, researchers were able to reach a stable 1.2 volts. (The voltage of a standard AA alkaline battery is 1.5 volts.) The battery’s performance decreased significantly after an hour when the paper dried. However, after two more drops of water were added, the battery maintained 0.5 volts for an additional hour.