A tubular, soft robot controlled by light can pump liquids, unscrew bolts and travel through pipes. The robot can also be designed to bend in the direction of a light source, like a plant tilting towards the sun. In some materials, molecules can gain energy from light, which makes the material expand or contract. Jiu-an Lv at Westlake University in China used this effect to create prototypes of a soft robot made up of a tube 15 to 40 millimetres long. He and his colleagues wound filaments of a light-sensitive elastic material into an arrangement inspired by an elephant's trunk, which has muscle fibres layered together in such a way that they can assume many different shapes depending on which ones get tense.