Emily Matchar in Smithsonian:
Electric eels, which slither along the muddy bottoms of ponds and streams in the Amazon and Orinoco river basins of South America, can cause a shock powerful enough to knock a horse off its feet. Their power comes from cells called electrocytes that discharge when the eel is hunting or feels threatened. Now, researchers are taking inspiration from these eels (not technically eels, as a matter of fact, but a type of fish) to develop new power sources that could one day power electrical devices in the human body, such as pacemakers, sensors and prosthetic organs. Electric eels can synchronize the charging and discharging of thousands of cells in their bodies simultaneously, says Max Shtein, a chemical engineer at the University of Michigan who worked on the research. “If you think about doing that very quickly – [in a] mere fraction of a second – for thousands of cells simultaneously, that’s a rather clever wiring scheme,” he says. The electrocytes of an electric eel are large and flat, with hundreds stacked together horizontally. Because of the way they’re stacked, the cells’ tiny individual voltages add up to a significant kick. This is possible because the surrounding tissue insulates the electrocytes so the voltage flows forward to the water in front of the fish – stunning or killing prey or threats – then flows back to create a complete circuit.
Shtein and his team tried to copy the eel’s physiology by creating about 2,500 units made of sodium and chloride dissolved in water-based hydrogels. They printed out rows of tiny multicolored buttons of hydrogels on long sheets of plastic, alternating the salty hydrogels with ones made just with water.