A robot made from gel bends in response to light, allowing for a wide variety of motions.

With a pulse of light, a slim strip of soft gel comes alive underwater and crawls, jumps and swims against the water’s drag.

Researchers led by Metin Sitti at the Max Planck Institute for Intelligent Systems in Stuttgart, Germany, sought to make soft robots that can move underwater. Inspired by the fluid motion of sea slugs, the scientists chose bending as the basis for their robot’s movements. They turned to liquid crystals as a basic material and light as a power source.

In liquid crystal displays such as those found in laptops, neatly aligned long molecules create images by moving in response to electric fields. Such molecules can also respond to light.

Sitti’s team introduced a plasticizer to a common type of liquid crystal, transforming it from a stiff substance into a flexible, soft gel. On illumination, long molecules that were lined up in loose rows within the gel splayed apart, forcing the gel to bend.

One robot walked some 65 millimetres on an underwater track in 108 seconds. Another propelled itself while bearing a thin frame roughly its own size.