Microbes live in our body, in the soil, in water and in waste. As they feed, they harvest electrons from the environment and then excrete them.
Many scientists have figured out how to capture those electrons in microbial fuel cells and turn them into a power source. But Seokheun "Sean" Choi, assistant professor and director of the Bioelectronics & Microsystems Lab the State University of New York, Binghamton, has figured out how to do it using paper.
His foldable, paper-based battery is a bacteria-powered fuel cell that could be used to run small biosensors. Because it's made from paper, the device is cheap and disposable. Because it runs on microbes, it can generate energy wherever and whenever it's needed.
"Theoretically, the microorganisms are everywhere. I thought that the bacteria-based battery could be activated even in the most resource-limited settings," Choi told Seeker.
This might mean using it in disaster areas, on the battlefield or in clinics that serve impoverished communities.
Fundamentally, Choi's battery has the two main components of all batteries: an anode, considered the negative end, and a cathode, considered the positive end. The anode is typically the source of the electrons, which flow to the cathode to create a current.
With this battery, Choi created an anode on one side of paper that's made of a tiny amount of bacteria-laden water housed in a reservoir formed in a conductive polymer. On the other side of the paper is the cathode, a ribbon of silver nitrate underneath a thin layer of wax.
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By folding the paper so that the two sides come into contact, electrons from the microbes flow toward the cathode to create an electric current. Folding the battery in different shapes varies the electrical output. For example, by crimping it accordion-style so that six rows of six fuel cells are touching, the battery produces 44.85 microwatts at 105.89 microamps.
Choi acknowledges that this is a very small amount of power. In the early days, when he first considered making paper electronics, he was skeptical they'd have any use. But then he realized that biosensors, like those that detect pathogens or monitor the blood sugar levels, didn't need much power to begin with. He also liked the idea of tapping a ubiquitous source of energy.
"Now, this work uses wastewater, but the devices can be workable with any liquid like body fluids, such as blood, sweat, urine, or saliva," he said.
This is not Choi's first paper battery. Earlier this year, his team introduced a design that folded up into a Ninja star-shaped frame.
The latest iteration is a step up from the star.
"This one is much more upgraded. You don't need to use many paper layers. All the components will be integrated into one sheet of paper," he said.
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