Researchers from the State University of New York, Binghamton, have developed a new type of battery made of paper and fuelled by bacteria, which could eventually become a portable, low-cost alternative for powering diagnostic devices in regions where commercial batteries are unavailable or too expensive.

Dr Seokheun Choi presented the study’s findings at the 256th National Meeting & Exposition of the American Chemical Society (ACS).

Choi said: “Paper has unique advantages as a material for biosensors. 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.”

Disposable paper-based biosensors have previously been developed as a cheap and convenient way to diagnose diseases and detect environmental contaminants. Many of these devices rely on colour changes to indicate results but they are often not sensitive enough. Choi and his team aimed to develop an inexpensive paper battery that could be easily incorporated into single-use biosensors to boost their sensitivity.

The paper battery is made by printing thin layers of metals and other materials onto a paper surface. Then, freeze-dried exoelectrogens are placed onto the paper. Exoelectrogens are a type of bacteria that can transfer electrons outside of their cells. These electrons are generated when the bacteria make energy for themselves and they pass through the cell membrane. They then make contact with external electrodes and power the battery. Water or saliva is required to activate the battery. Within a couple of minutes, the liquid revives the bacteria, which have been shown to produce enough electrons to power a light-emitting diode and a calculator.

Choi said: “The power performance also needs to be improved by about 1,000-fold for most practical applications.” He thinks this could be achieved by stacking and connecting multiple paper batteries.

The effect of oxygen on the device was also tested. Oxygen was found to soak up the bacteria’s electrons before they reached the electrode which slightly decreased the device’s power generation abilities. However, this effect was minimal.

Currently, the battery can only be used once and has a shelf-life of about four months. Choi and his team are working to improve the survival and performance of the freeze-dried bacteria, with the aim of creating a longer shelf-life.

A patent for the paper battery has been applied for and Choi is seeking industry partners for commercialisation.