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August 08, 2011

Tunable metallic-like conductivity in microbial nanowire networks


The discovery of a fundamental, previously unknown property of microbial nanowires in the bacterium Geobacter sulfurreducens that allows electron transport across long distances could revolutionize nanotechnology and bioelectronics This may one day lead to cheaper, nontoxic nanomaterials for biosensors and solid state electronics that interface with biological systems. Networks of bacterial filaments, known as microbial nanowires because they conduct electrons along their length, can move charges as efficiently as synthetic organic metallic nanostructures, and they do it over remarkable distances, thousands of times the bacterium’s length.

Nature Nanotechnology - Tunable metallic-like conductivity in microbial nanowire networks



Electronic nanostructures made from natural amino acids are attractive because of their relatively low cost, facile processing and absence of toxicity. However, most materials derived from natural amino acids are electronically insulating. Here, we report metallic-like conductivity in films of the bacterium Geobacter sulfurreducens and also in pilin nanofilaments (known as microbial nanowires) extracted from these bacteria. These materials have electronic conductivities of about 5 mS cm−1, which are comparable to those of synthetic metallic nanostructures. They can also conduct over distances on the centimetre scale, which is thousands of times the size of a bacterium. Moreover, the conductivity of the biofilm can be tuned by regulating gene expression, and also by varying the gate voltage in a transistor configuration. The conductivity of the nanofilaments has a temperature dependence similar to that of a disordered metal, and the conductivity could be increased by processing.


Fig. S1| Top view 3-D projection of fluorescent confocal laser microscopy
images of split electrodes illustrating a lack of biofilm on the control electrodes not connected to cathode. Fig. S2| Top view 3-D projection of fluorescent confocal laser microscopy images of split electrodes when only one of the two electrodes was connected to the cathode


12 pages of supplemental material

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