Eel-y shocking power source

The electric eel can generate electrical discharges of 100 watts to stun prey, but should you X-ray an eel, you wouldn’t find a battery pack inside. Instead, thousands of cells called electrocytes are arranged along its body, each producing a small ion gradient and therefore a potential difference across them. Now, Michael Mayer and colleagues have developed a hydrogel-based system that mimics the electrocyte mechanism and could be used as a soft power source for robotics. They arrange sets of ion-selective hydrogels in series to generate ion gradients across a group of four hydrogel droplets. These droplets can either be arranged in series in a microfluidic set-up, or be stacked in parallel by folding up an array of hydrogels using origami principles. The net result is a power source that is able to generate voltages similar to those generated by the electric eel.