Bacteria-powered batteries activated by human spit

US researchers have developed a battery activated by human spit, which can be used in extreme conditions where normal batteries don’t function. Published in the journal Advanced Materials Technologies, their work is the culmination of five years of research into micro-power sources for use in resource-limited regions to power point-of-care (POC) diagnostic biosensors.

As explained by Seokheun Choi, an assistant professor at Binghamton University and co-author on the research, “On-demand micro-power generation is required especially for point-of-care diagnostic applications in developing countries. 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 overqualified. Also, they pose environmental pollution issues.”

Along with research assistant Maedeh Mohammadifar, Choi created a high-performance, paper-based, bacteria-powered battery by building microbial fuel cells (MFCs) with inactive, freeze-dried exoelectrogenic cells, which generates power within minutes of adding saliva. The proposed battery generated reliable power with one drop of saliva, supplying onboard power that could be used by the next generation of disposable, paper-based POC diagnostic platforms.

“The proposed battery has competitive advantages over other conventional power solutions because the biological fluid for on-demand battery activation is readily available even in the most resource-constrained settings, and the freeze-drying technology enables long-term storage of cells without degradation or denaturation,” the researchers wrote.

According to Choi, the battery’s power density is currently a few microwatts per square centimetre. He and his colleague are now focused on improving this so that more applications can be powered.

“Although 16 microbial fuel cells connected in a series on a single sheet of paper generated desired values of electrical current and voltage to power a light-emitting diode (LED), further power improvement is required for other electronic applications demanding hundreds of milliwatts of energy,” he said.

Image credit: Seokheun Choi.