Metallic-Like Conductivity

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UMASS-Amherst researchers report in the latest issue of Nature Nanotechnology that the microorganism Geobacter produces nanowires that transfer electrons via a mechanism not previously observed in biological materials.  Electrons move through the protein filaments with a metallic-like conductivity.  Networks of the filaments permit Geobacter to produce films that are highly conductive and can transfer electron over cm distances.  These findings explain novel environmental properties of Geobacter, such as it ability to grow on iron minerals in soils and sediments where it plays an important role in removing contaminants from groundwater.  The metallic-like wires are key to bioenergy applications of Geobacter, which plays an important role in the conversion of wastes to methane in large-scale wastewater digestors, or for generating electricity from wastes in microbial fuel cells, a useful bioenergy strategy for remote locations.  Furthermore, the production of a self-sustaining conductive material, grown from inexpensive materials like acetic acid, that is “tunable” by changes in gene expression and also by gate voltage in a transistor configuration opens new possibilities for the generation of environmentally-sustainable nanomaterials and nanoelectronic devices.

 

Photos

Geobacter and its nanowire network


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Network of microbial nanowires in biofilms grown in a microbial fuel cell
(Image credit: Nikhil Malvankar and Ching Leang)
Standing from left: Mark Tuominen, Ching Leang, Ashley Franks, Kelly Nevin
Sitting from left: Madeline Vargas, Nikhil Malvankar, Vince Rotello, Derek Lovley

Click to view high resolution

Click to view high resolution

Scanning electron microscopy (SEM) images of biofilmsgrown on split-gold Electrodes
(Image credit: Nikhil Malvankar and Dale Callaham)
SEM images of critical-point dried biofilm. The region represented by a circle in the left image is magnified in the right image.

Schematic of  four-anode microbial fuel cell

Schematic of  measurement setup

Conductivity was measured using two and four-probe approach and also using DC current-voltage and AC impedance spectroscopy methods.  For conductivity measurements, anodes and cathode were temporarily disconnected. Electrodes were connected to electronics to study electrical properties of live biofilms
More on the Process

Nikhil Malvankar measuring the properties of biofilms and nanowires.

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