A thousand-strong army of coin-sized robots (pictured) can arrange itself into various configurations.

Credit: Michael Rubenstein, Harvard Univ.

Michael Rubenstein and his co-workers at Harvard University in Cambridge, Massachusetts, programmed 1,024 robots with a simple set of rules and an image of a shape to be formed. Four 'seed robots' act as a point of origin for a coordinate system and send their coordinates to neighbours using infrared light. This information spreads through the group, allowing each robot to determine its relative location in the swarm.

The robot flock can form programmed shapes — such as the letter 'K' — in around 12 hours and is the largest yet to demonstrate collective behaviour, the authors say.

Science 345, 795–799 (2014)