Although biodegradable, disposable electronic devices such as environmental sensors are now available, the batteries that power these devices still pose an ecological problem.
To this end, scientists at Singapore's Nanyang Technological University (NTU) have developed a paper-based biodegradable battery designed to provide a sustainable option for powering wearable electronic devices. The team says the finished battery, which is about 0.4 millimeters thick, is completely broken down by microbes within a month of being placed in the soil. The results of this study have recently been published in Advanced Science.
In a proof-of-concept experiment described by Advanced Science, researchers demonstrated how a 4cm x 4cm square printed paper battery could power a small electric fan for at least 45 minutes. Bending or twisting the battery did not interrupt power.
In another experiment using a 4cm x 4cm battery to power an LED, the scientists showed that the LED remained lit despite cutting off part of the paper battery, indicating that the cut did not affect the battery's function.
It is understood that the core of this battery is a cellulose paper, which is reinforced by a hydrogel to fill the gaps between the cellulose fibers. This paper serves as a separator between the two electrodes - anode and cathode - which are screen printed on both sides of the paper. The conductive ink used for printing the anode consists mainly of zinc and carbon black, while manganese and nickel are used for the cathode ink, respectively. After the electrostamping process is completed, the entire cell is immersed in an electrolyte solution, after which a thin layer of gold is applied to the two electrodes to increase their conductivity.
"When decomposition occurs, the electrode material is released into the environment," said Professor Fan Hongjin, "and the nickel or manganese used in the cathode will remain in its oxide or hydroxide form, which is close to the form of the natural mineral. The zinc found in the anode will be naturally oxidized to form a non-toxic hydroxide. This suggests that the battery has the potential to be a more sustainable alternative to current batteries." Fan is said to be leading the research along with Assistant Professor Lee Seok Woo.
