BOSTON, Aug. 19, 2018 -- In remote areas of the world or in regions with limited resources, everyday items like electrical outlets and batteries are luxuries. Health care workers in these areas often lack electricity to power diagnostic devices, and commercial batteries may be unavailable or too expensive. New power sources are needed that are low-cost and portable. Today, researchers report a new type of battery -- made of paper and fueled by bacteria --- that could overcome these challenges.
The researchers will present their results today at the 256th National Meeting & Exposition of the American Chemical Society (ACS). ACS, the world's largest scientific society, is holding the meeting here through Thursday. It features more than 10,000 presentations on a wide range of science topics.
"Paper has unique advantages as a material for biosensors," says Seokheun (Sean) Choi, Ph.D., who is presenting the work at the meeting. "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."
Researchers have previously developed disposable paper-based biosensors for cheap and convenient diagnosis of diseases and health conditions, as well as for detecting contaminants in the environment. Many such devices rely on color changes to report a result, but they often aren't 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.
So Choi and his colleagues at the State University of New York, Binghamton made a paper battery by printing thin layers of metals and other materials onto a paper surface. Then, they 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 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. The team found that although oxygen slightly decreased power generation, the effect was minimal. This is because the bacterial cells were tightly attached to the paper fibers, 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 says. 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 commercialization.
The researchers acknowledge support and funding from the National Science Foundation, the Office of Naval Research and the Research Foundation for the State University of New York.
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Merging Electronic Bacteria with Paper
The next generation of electronics requires new device platforms that can be integrated with non-planar surroundings for the emerging Internet-of-Things (IoT) and be environmentally-friendly to reduce the dramatic increase in electronic waste (e-waste). Paper-based electronics (papertronics) have been recently considered as one of the most exciting device platforms because of their flexibility, sustainability, eco-friendliness, and low cost as well as their excellent mechanical, dielectrical and fluidic properties. Now, innovative structure engineering techniques can manipulate diameters of the cellulose fibers of paper, smoothing the roughness and controlling the transparency for numerous device applications. Novel functionalization techniques of paper with organic, inorganic, and biological entities enable many engineering possibilities, revolutionizing papertronics for the next generation of electronics. Among those techniques for new functionalities, integrating electric bacteria into paper has attracted considerable interest as a new energy technique for papertronics. Paper has unique synergistic characteristics including a porous and hydrophilic environment for bacterial viability, a high surface area for bacterial accumulation, and sustainability even in resource-limited settings. A simple, paper-based device can use the respiration of electric bacteria to harvest electrons. In this work, we pursued comprehensive analytical and experimental approaches to provide a novel but realistic and accessible power source from bacteria loaded into paper. This report provides new approaches to revolutionarily activate the biobattery and significantly improve its shelf life. Furthermore, we ensure for the first time the practical efficacy of the explored technique, generating on-demand energy even in resource-limited environments to power a light-emitting diode and an electric calculator.