Researchers from the University of Massachusetts Amherst, with funding from the Office of Naval Research (ONR) have worked out a biological method to produce the smallest electrical wires you’ve ever seen. Or rather, haven’t seen because they’re microscopic. It’s thanks to a clever tweak to the genetic code of a common soil bacterium that causes it to spit out conductive filaments thousands of times thinner than a human hair.The organism in question is known as Geobacter. There are a number of significant species of this bacterium, many of which are notable for their ability to oxidize metals, petroleum compounds, and radioactive materials into mostly harmless carbon dioxide. Key to this ability is Geobacter’s production of protein-based conductive nanowires. You can probably see where this is going.The wild-type organism produces nanowires that carry enough current to sustain its own biological processes, which isn’t enough for scientists to make use of in the lab. However, The University of Massachusetts team led by Dr. Derek Lovley modified the bacteria’s DNA to make the nanowires more robust. The genetic tweak adds more of the amino acid tryptophan by swapping out two structurally similar amino acids in the nanowire. Tryptophan is better at carrying a current than other amino acids, so it increases the capacity of the nanowire without increasing its size.The results of the experiment were far better than the team was expecting. The tryptophan-infused nanowires were 2,000 times more conductive than their unmodified form. They retained the extremely small diameter (1.5 micrometers, 60,000 times smaller than a human hair), allowing huge networks of nanowires to be used in a very small space. These biological nanowires could be used in electronic devices, to create biological fuel cell networks, or chemical sensors. Key to this will be stabilizing the proteins in the nanowires, which won’t be as stable as wires made from non-biological components. The ONR plans to continue funding this work.
September 1, 2019