AMHERST, Mass. – Stephen S. Nonnenmann, assistant professor of mechanical and industrial engineering at the University of Massachusetts Amherst, is part of a team of researchers that created a “quantum material” that mimics a shark’s ability to detect the minute electric fields of small prey. The new sensor performs well in ocean-like conditions and opens the way for potential uses ranging from defense to marine biology. The findings were published in the Jan. 4 issue of Nature.
The researchers say this new technology might be used to study ocean organisms and ecosystems and to monitor the movement of ships for military and commercial maritime applications. The new material maintains its functional stability and does not corrode after being immersed in saltwater, a prerequisite for ocean sensing. It also functions well in the cold, ambient temperatures typical of seawater, they say.
The research team includes scientists at Purdue University, who headed the effort, along with colleagues from the Argonne National Laboratory, Rutgers University, the National Institute of Standards and Technology, the Massachusetts Institute of Technology, the Canadian Light Source at the University of Saskatchewan, Columbia University and UMass Amherst. The study was headed by Shriram Ramanathan, professor of materials engineering at Purdue. Graduate student Derek Schwanz and postdoctoral student Zhen Zhang of the Ramanathan group created a material capable of transporting ions from the surrounding water to serve as a sensor.
The new sensor was inspired by an organ near a shark’s mouth called the ampullae of Lorenzini, which is capable of detecting small electric fields from prey animals. “This organ is able to interact with its environment by exchanging ions from seawater, imparting the so-called sixth sense to sharks,” Zhang says. The material they developed for the sensor is called samarium nickelate, which is a quantum material, meaning its performance taps into quantum mechanical interactions. Samarium nickelate is in a class of quantum materials called strongly correlated electron systems, which have exotic electronic and magnetic properties.
Nonnenmann and his group working in the Nanoscale Interfaces, Transport and Energy laboratory at UMass Amherst used their expertise in atomic force microscopy (AFM), a nanoscale characterization technique, to help the team from Purdue determine to what extent protons diffused into the oxide material of the sensor.
“AFM records the topography of a surface similar to a fancy record player,” Nonnenmann says. “And if the record needle is conductive, we can determine local changes in conductivity within the sample.”
Jiaxin Zhu, a doctoral student in mechanical engineering at UMass Amherst, used this conductive AFM technique on the cross-section of the quantum material to observe areas of low conductivity in the film region adjacent to the saltwater-exposed region. Their results helped confirm that the oxide quantum material undergoes a phase change when exposed to water, thus changing from a conductor to an insulating, non-conductive material. “This is a very important and exciting discovery,” says Nonnenmann, “and really opens up new possibilities to interface functional inorganic materials with bio-related entities in aqueous environments and remain stable.”