‘Quantum’ sensor mimics shark’s ability to detect tiny electric fields

Technology News | December 19, 2017

By Rich Pell

Inspired by an organ near a shark’s mouth, the sensor can detect minute electric fields – similar to the way sharks are able to detect their prey in the ocean. According to the researchers, their sensor has been shown to perform well in ocean-like conditions, and offers potential in applications ranging from energy and defense to marine biology.

Not only does the material maintain its functional stability and not corrode from being immersed in saltwater, it also functions well in cold, ambient temperatures such as those typical of seawater. As a result, say the researchers, it potentially has very broad usefulness in many disciplines, from studying ocean organisms and ecosystems to monitoring the movement of ships for military and commercial maritime applications.

The sensor works in a similar way to a shark’s special sensing organs – called electroreceptors – which interact with their environment by exchanging ions from seawater. The organs contain a jelly that conducts ions from seawater to a specialized membrane – located at the bottom of each organ – that contains sensing cells allowing the shark to detect bioelectric fields emitted by prey fish.

The researchers created their sensor using a quantum material called samarium nickelate. Special properties of the material, such as its ability to conduct protons very fast, caught the researchers’ interest in it as a possible sensor that could mimic the shark’s organ.

“We have been working on this for a few years,” says Shriram Ramanathan, a Purdue professor of materials engineering. “We show that these sensors can detect electrical potentials well below one volt, on the order of millivolts, which is comparable to electric potentials emanated by marine organisms. The material is very sensitive. We calculated the detection distance of our device and find a similar length scale to what has been reported for electroreceptors in sharks.”

According to the researchers, the quantum effect causes the material to undergo a dramatic “phase change” from a conductor to an insulator, which allows it to act as a sensitive detector. The material also exchanges mass with the environment, as protons from the water move into the material and then return to the water, going back and forth.

A traditional material, such as aluminum, reacts when placed in seawater, forming an oxide coating that prevents further interaction with its environment. In this case, the researchers say, they are starting with the oxide material and maintaining its functionality.

The researchers’ material also changes optical properties, becoming more transparent as it becomes more insulating. As a result, its properties can be studied both electrically and optically.

The researchers tested the material by immersing it in a wide range of simulated ocean water environments, designed to simulate those found across the earth’s oceans. The nest step, they say, is to test it in real real oceans.

For more, see “Perovskite nickelates as electric-field sensors in salt water.”