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You’d need your glasses on to play this version of Pac-Man. Tiny metal robots can plot their own route around a maze modelled on the iconic video game. Similar devices could one day be used to travel around the body, delivering drugs or performing surgery.

Sarthak Misra from the University of Twente, the Netherlands, and colleagues created four different types of micro-gripper robots, with the smallest being just 100 micrometres long. The biggest was still less than one millimetre. The bots are made from metal and controlled using magnetic fields and have have…