Tiny soft robots can swim, spin and make other complex motions in response to light.

Microbots — micrometre-scale robots — could one day be used to deliver medicines or to collect data inside the body. But most microbots are made of rigid materials, which limit them to simple back-and-forth motions, usually in response to chemical or magnetic forces. To develop microbots that are capable of more-versatile movement, Peer Fischer at the Max Planck Institute for Intelligent Systems in Stuttgart, Germany, and his colleagues designed soft, flexible ones using a liquid-crystal elastomer that was both rubbery and responsive to light.

By sweeping bands of light across disc- and rod-shaped microbots, the team induced wave-like swimming motions similar to those used by single-celled organisms. Different patterns of light also made the disc-shaped microbots spin, reverse their spinning direction or move around a path in the shape of a square.

Nature Mater. http://doi.org/bcjk (2016)