Paper-based bio-battery powered by bacteria
Image credit: State University of New York.
A new type of battery made of paper and fuelled by bacteria has been developed by researchers at the State University of New York.
“Paper has unique advantages as a material for biosensors,” said Seokheun Choi who worked on the project. “It is inexpensive, disposable, flexible and has a high surface area. However, sophisticated sensors require a power supply. Commercial batteries are too wasteful and expensive and they can’t be integrated into paper substrates. The best solution is a paper-based bio-battery.”
The battery draws inspiration from earlier technologies such as disposable, paper-based biosensors which are used to diagnose diseases and health conditions, as well as for detecting contaminants in the environment.
Many such devices rely on colour changes to report a result and are often not very sensitive. To boost sensitivity, the biosensors need a power supply. Choi wanted to develop an inexpensive paper battery powered by bacteria that could be easily incorporated into these single-use devices.
The battery is created by printing thin layers of metals and other materials onto a paper surface. The research team then placed freeze-dried “exoelectrogens” on the paper. Exoelectrogens are a special type of bacteria that can transfer electrons outside of their cells.
The electrons, which are generated when the bacteria make energy for themselves, pass through the cell membrane.
They can then make contact with external electrodes and power the battery. To activate the battery, the researchers added water or saliva. Within a couple of minutes, the liquid revived the bacteria, which itself produced enough electrons to power a light-emitting diode and a calculator.
The researchers also investigated how oxygen affects the performance of their device. Oxygen, which passes easily through paper, could soak up electrons produced by the bacteria before they reach the electrode.
They found that although oxygen slightly decreased power generation, the effect was minimal. This is because the bacterial cells were tightly attached to the paper fibres, which rapidly whisked the electrons away to the anode before oxygen could intervene.
The paper battery, which can be used once and then thrown away, currently has a shelf life of about four months.
Choi is working on conditions to improve the survival and performance of the freeze-dried bacteria, enabling a longer shelf life.
“The power performance also needs to be improved by about 1,000-fold for most practical applications,” Choi said. This could be achieved by stacking and connecting multiple paper batteries, he notes. Choi has applied for a patent for the battery and is seeking industry partners for commercialisation.