Nano-sized conductive wires built by bacteria
Over the years, the Office of Naval Research (ONR) has produced some impressive innovations, from unmanned sub-chasing ships to self-healing paint for armored vehicles. Now, it's turned its attention towards producing new electrical materials, by looking to, and even improving upon nature.
The new research is led by Dr Derek Lovley, head of a team at the University of Massachusetts Amherst, sponsored by the ONR. The work focuses on a bacteria called Geobacter, which produces microbial nanowires.
These protrude from the organism, letting it form electrical connections with iron oxides in the ground, helping it to grow. That electrical conductivity is useful for the bacteria, but in its natural state, is too weak for humans to make use of.
"As we learned more about how the microbial nanowires worked, we realized it might be possible to improve on nature's design," said Dr Lovley. "We rearranged the amino acids to produce a synthetic nanowire that we thought might be more conductive."
The researchers adjusted the genetic makeup of the bacteria, replacing two naturally occuring amino acids with tryptophan – another amino that's famous for allegedly causing sleepiness when consumed, but that's extremely effective at transporting electrons.
Upon testing, the modified Geobacter hugely surpassed the expectations of the team, with the tryptophan-infused nanowires being some 2,000 times more conductive than the naturally occurring wires. They were also even smaller than their natural counterparts, with a diameter of just 1.5 nanometers (equivalent to 60,000 times thinner than a human hair), and they were more durable.
While it's certainly early days, there are a huge number of potential uses for the tiny wires. For example, their size could make them perfect for use in medical sensors, and the researchers claim that they could be used to feed electrical currents to microbes engineered to produce butanol – an alternative fuel source.
"This is an exciting time to be on the cutting edge of creating new types of electronics materials," said Lovley. "The fact that we can do this with sustainable, renewable materials makes it even more rewarding."