Black Ghost Electric Knifefish Inspire Underwater Robots

The black ghost knifefish, a tropical electric creature from South America, offers novel ideas for underwater robotics.

Inspired by this jet black fish, researchers at the Northwestern University developed an agile fish robot to help in undersea operations like examining debris of sunken ships, studying  fragile coral reefs and repairing damaged deep-sea oil rigs.

The nocturnal black ghost knife fish use an electric current and a fin to find their way around the darkest sea regions. It can produce as well as sense the electrical impulses as it swims in multiple directions. Using a ribbon like fin, it moves both forward and backward.

They are mainly found in the Amazon Basin, Peru and fast-moving sandy bottom creeks in tropical climates. "Our technology for working in water is not very advanced," said MacIver, a robotics expert who has studied the black ghost knifefish for two decades. "Current underwater vehicles are large and lack agility, which means that working close to living or humanmade structures, is nearly impossible. We've taken lessons learned from the knifefish about movement and non-visual sensing and developed new technologies that should improve underwater vehicles."

Prof. Maclver noticed that these fish generate an electric field from the neurons present in their spinal cord. When a prey wanders into their field, the fish can measure a small change in the voltage on the skin's surface that is one-tenth to one-hundredth of a million of volt,  adequate enough for the receptors to detect it, reports  BBC.

"The fish have evolved an amazing system," said Prof, MacIver. "Imagine your retina stretched over your entire body and what that would be like. That's the situation that knifefish find themselves in. They perceive in all directions. They emit a kind of radar, but it's an electric field; and the sensory receptors scattered over their entire body surface mean they can detect things coming from all directions."

The team is replicating the same properties in a robot designed to react to the surrounding environment.  Using these properties including its unique propulsion technique, the team has created over half a dozen robots.

The research will be presented at the American Association for the Advancement of Science (AAAS) annual meeting in Chicago.