Engineers Take Cues from Beetles to Make a Super-Efficient Robo-Boat

Dolphins are elegant swimmers, but waterlily leaf beetle larvae take first place for the simplest stroke. The insect just arches its back to manipulate a basic physics principle that lets it glide across water. Now engineers have borrowed this technique to make a tiny boat that could autonomously patrol water reservoirs for months on just a watch battery.

The larva's efficiency relies on surface tension, the force that causes water molecules to stick together. By arching its body, the larva disrupts the water's tension in such a way that the bug moves forward. Sung Kwon Cho, an engineer at the University of Pittsburgh, decided to harness the tension, like the beetle does, to move an inch-long boat. But instead of making a bendable craft, Cho attached a Teflon-coated electrode to the plastic boat's stern.

Video courtesy Sang Kung Chung, Kyungjoo Ryu, and Sung Kwon Cho

Teflon usually repels water, but when you charge it with electricity it breaks the surface tension, as the beetle does, to push the boat along. A side-mounted electrode turns the boat. Cho suggests that his device could be up to 100 times as efficient as mechanically driven mini-boats and, in a few years, could scale up to power a sensor-toting surveillance dinghy five times the size of his prototype.