Mini fuel cell with bio-drive

Researchers are developing biofuel cells to power miniature machines in their bodies

Schematic of a future mini-probe with biofuel cell © RUB
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Self-propelled minisons floating in our bloodstream are still science fiction today. But the first prerequisites for this have already been created by scientists. They developed a miniature fuel cell that uses the body's own molecules as a raw material and could once serve as a drive for mini-probes.

Alarm in the bloodstream near the heart: A heart attack threatens. Immediately tiny repair machines are activated, which remove the incipient vein occlusion of the coronary arteries. Is this scenario just science fiction? Not quite. For the first step on the long road to miniature biofuel machines, which do their work in the human body, is already happening. At the Center for Electrochemistry, Professor Wolfgang Schuhmann and his team are researching to develop miniaturized fuel cells that are completely driven by the substances present in the blood. This technique could someday be the engine of miniature machines.

Small cell, big challenge

For the vision of a blood-powered fuel cell in the human body, researchers must overcome a variety of problems. The key challenge: biofuel cells must be very small, yet powerful. Due to the small size, the electrodes can not be enclosed in separate compartments because the volume of the wall would be disproportionately large in relation to the volume of the entire cell. In turn, a wall-less cell requires that the anode and cathode function in the same medium.

Prototype of a biofuel cell © RUB

The secret for the construction of such a powerful biofuel cell lies in the construction of the electrode materials. Even with the currently available material combinations, the biofuel cell of the Bochum electrochemist meets all requirements and achieves an output of 0.1 milliwatts per square centimeter. Thus, the researchers are only one power of ten away from the target of one milliwatt per square centimeter.

"Nano forest" made of carbon tubes

For the biofuel cells, the researchers first prove graphite electrodes with biocatalysts (enzymes), which provide for the exchange of electrons with substances present in the blood. To increase the flow of electrons, a large number of enzymes are bound to a three-dimensional device (redox polymer) that efficiently conducts electrons between the electrode and the enzyme. display

In order to increase the usable area, Schuhmann's team is also experimenting with carbon nanotubes, which cover the electrode surface like a forest. The next goal of the researchers is to equip the nano-forest with redox polymers. Initial tests with "nanoforne" coated electrodes without redox polymer already showed a 400-fold increase in electron flow compared to systems without nanotubes. The way to deployable mini-machines is still far from here, but the first steps have already been taken.

(Ruhr-University Bochum, 20.05.2010 - NPO)