Spit on this: Tiny power generator utilizes unexpected fuel source in human saliva


A fuel cell running on human saliva can generate tiny but sufficient amounts of power to run applications on a chip, possibly leading to implantable biomedical electronics, researchers say.

The power is created as bacteria common in saliva cause organic material to break down, which produces a charge that is transferred to an anode in the device, they say.

By producing nearly 1 microwatt in power, this saliva-powered, micro-sized MFC (microbial fuel cell) already generates enough power to be directly used as an energy harvester in microelectronic applications, said engineers at Penn State, who worked with colleagues at King Abdullah University of Science and Technology in Saudi Arabia. The study was reported in the Nature Publishing Group's journal Asia Materials.

Penn State environmental engineering Professor Bruce Logan credits researcher Justine E. Mink at the King Abdullah University with the original idea.

"The idea was Justine's because she was thinking about sensors for such things as glucose monitoring for diabetics and she wondered if a mini microbial fuel cell could be used," Logan says. "There is a lot of organic stuff in saliva."

Scientists have been working to develop power sources for biomedical electronics that could run low-power, on-chip applications.

For example, such technology could lead to a miniature ovulation predictor that could monitor conductivity in a woman's saliva, which undergoes changes around five days prior to ovulation.

The predictor could both record the conductivity in the saliva while using the saliva as a power source to communicate the data to a cell phone.

Additional applications could yield lab-on-a-chip devices and point-of-care diagnostics.

"Our study is the first to show that saliva (and most probably other highly concentrated organic fuels) can be used to power bioelectronics devices," King Abdullah University researcher Muhammad Hussain says. "By producing nearly 1 microwatt of power, our micron-sized MFC is already good enough to run ultralow power lab-on-a-chip devices -- such as an EEG seizure detection system, to name but one example."

The researchers say they've tested the mini fuel cell with both human saliva and acetate, but say it can utilize any liquid containing sufficient amounts of organic material.

While waste material has often been used to power such devices, using saliva as a fuel brings them into the realm of implantable medical devices, they say.

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