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.
Instead of the robot’s fibres responding to electrical signals from the brain, like in an elephant, they responded to light. When illuminated with light of different frequencies and intensities, the robot took on different shapes.
In one experiment, the researchers filled the robot with a liquid and connected it to a tube that led to a raised container. Using light to make the robot contract pumped the liquid upwards and into the container. In another, they slid the robot through a curved pipe that had a bolt at the bottom. When its bendy body connected to the bolt, the researchers illuminated it to make it twist and unscrew the bolt.
But Lv is most excited about an experiment where they worked out how to wind the light-sensitive fibres into the shape of an artificial plant that combined the bending and twisting motions to move towards light. When the light was very intense, the robot could also tilt away from it.
Shengqiang Cai at the University of California, San Diego, says that this adaptive behaviour is impressive and may be useful for developing devices that can keep adjusting themselves as they absorb and collect the energy of the sun.