“Build” is a bit sensational, as it implies nanomachines self-replicating. This is not nearly that. It is simply a gel material that uses the fish’s body to spread, solidifies into a flexible material, and is conductive. It has the potential of being non-invasive and non-inflammatory. I would change the title to:
“Electrodes constructed using body’s own chemistry inside of live fish”
Much more accurate.
Anyway, neat.