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Researchers at Binghamton University, in New York, have developed a bacteria-powered battery which is activated by saliva. The batteries were designed by Binghamton University Electrical and Computer Science Assistant Professor Seokheun Choi and are intended for use as micro-power sources in conditions where normal batteries are not ideal. Choi envisions them used to power point-of-care diagnostic biosensors in resource-limited regions. Says Choi, “Typically, those applications require only several tens of microwatt-level power for several minutes, but commercial batteries or other energy harvesting technologies are too expensive and … pose environmental pollution issues.”

Choi, and research assistant Maedeh Mohammadifar, created the paper-based, bacteria-powered battery by using inactive, freeze-dried exoelectrogenic cells (a microorganism capable of transferring electrons) to create microbial fuel cells. The cells are activated by adding saliva, and can generate power with as little as one drop of spit. The freeze-drying allows long-term storage of the fuel cells without degradation, making them especially useful for providing power to disposable, paper-based diagnostic platforms. Earlier versions of the bacteria-powered batteries were activated with dirty water. The next step will be to improve the battery’s power density to allow greater application. Choi has linked 16 microbial fuel cells in a series on a single sheet of paper to generate enough electrical current and voltage to power a light-emitting diode (LED). However, further power improvement will be needed to meet the demands of a wider range of electronic applications.

Developments in innovative fuel cell technology have already seen an implantable medical device that draws power directly from the human body and a smartphone battery that can charge in five minutes. What will be the next revolution in battery technology?