How does the body produce electricity

Nanogenerator can generate enough power for implanted sensors to measure blood pressure and sugar levels

Prototype of the combined power plant (graphic)

Atlanta (USA) - In the future, implanted mini-sensors could monitor body functions such as blood pressure or sugar levels. In order to supply these modules with electricity, scientists have now developed a tiny power plant that - also implanted - could make batteries superfluous. As they report in the journal "Angewandte Chemie", their first prototype consists of a bio-fuel cell and a generator that uses movement to generate electricity.

"In living organisms there is only mechanical and biochemical energy," explain Zhong Lin Wang and his colleagues from the Georgia Institute of Technology in Atlanta. They want to tap into precisely these two sources with their tiny combined cycle power plant in order to obtain small amounts of electricity. To do this, the researchers grew layers of zinc oxide nanowires along a filigree carbon fiber carrier. Pressure fluctuations in a flow of liquid - such as in pulsating blood vessels - were sufficient to generate three volts at 100 nanoamps. The so-called piezoelectric effect of zinc oxide was used for this, in which mechanical movements generate a flow of current. In order to generate electricity from biochemical energy, the researchers supplemented the mini power plant with a bio fuel cell. They placed special electrodes at one end of the carbon fibers in order to "harvest" electricity with a further 100 nanoampere at 0.1 volts from a biochemical reaction of sugar molecules.

However, this technology is not yet ready for use in the body. The first prototype of the combined power plant, which is still a few centimeters long, would have to shrink further. If this step is successful, however, a power generator could be attached to the wall of a blood vessel in the future. This power plant would be fed both by the regular pressure fluctuations in the blood circulation and by the sugar molecules contained in the blood. In medicine, the way to this application is still very long. But even before that, such power plant modules could be used in oil or gas pipelines in order to measure pressure and flow rates independently.