Sharks' electric field "sixth sense" could inspire better fuel cells

shark skin
CC BY 2.0 malkusch

Scientists and engineers are constantly looking to nature to find inspiration for better ways to do things and better materials to do them with. Plants, the original and best solar cells, are always being studied to improve solar technology, and animals have inspired a host of robots with their wide range of movements.

The latest amazing find in nature that is leading to biomimicry is the discovery of a highly conductive material in the organs of sharks and rays that lets them sense the electric fields of their prey.

It's long been known that sharks and rays have organs called the ampullae of Lorenzini that allow them to detect the weak electric fields of animals near them and find prey even in the dark depths of the ocean, but scientists haven't been able to figure out how exactly the organs work. A new study by researchers at the University of California Santa Cruz, University of Washington, and the Benaroya Research Institute at Virginia Mason has found that within these organs, which are like pores located around the head and along the underside of the animals, is a clear viscous jelly.

When the researchers studied the jelly they found that is highly conductive. In fact, it has the highest proton conductivity every reported of a biological material.

As the UC Santa Cruz explains, "Proton conductivity is the ability of a material or solution to conduct protons (positive hydrogen ions). In a system with very many ordered hydrogen bonds, such as a hydrated hydrophilic polymer, proton conduction can occur along chains of these bonds."

Currently there are proton-conducting polymers used in things like fuel cells where the polymer acts as the proton exchange membranes. The most highly performing polymer is called Nafion and the researchers found that the jelly from the electro-sensory organs was only 40 times less conductive that the man-made version.

"The first time I measured the proton conductivity of the jelly, I was really surprised," said first author Erik Josberger, an electrical engineering doctoral student in Rolandi's group at UW. "I didn't expect a natural material to approach the proton conductivity of an engineered material like Nafion."

The researchers plan to continue investigating this material and try to understand more about how it works within the animals' bodies to transmit these electric signals. They think that uncovering more information about the jelly could lead to new types of sensor technology and better, more efficient fuel cells.

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