New Material Spontaneously Moves, Forms Crystal-Like Patterns

The discovery of an internationals team of physicists marks an important step towards developing biology-inspired multifunctional robots. Connected robotic elements together form a new material, that 'dances' to an internal rather than an external beat. The repetitive back-and-forth movement of this material creates a stable oscillation also called 'time crystals'. Physicists from Amsterdam, Leiden and the UK made structures like this in two different forms: a one-dimensional ring and a two-dimensional surface. Their groundbreaking results are published in Nature today.

Combining crystal structures with active matter

Table salt and diamonds all have something in common: their atoms form a regular, repeating pattern in space. These materials are known as 'spatial crystals'. Lately, physicists have been very interested in an alternative option: that of time crystals; structures that also repeat a pattern in time.

This international team of researchers has created such time crystals ánd combined them with another hot topic in recent physics research: active matter. Configurations of interacting particles internally powered by their own source of energy. Its 'particles' need not be atoms of molecules; one example at a much larger scale is a flock of birds that together behave as one active unit.

Elastic and stable at the same time

'This paper shows that active elastic metamaterials are a gold mine of new physics', explains professor emeritus Theoretical Physics Wim van Saarloos. 'In our experiment, we observed a new way in which their movements change and grow in size, like waves. This process can lead to the spontaneous formation of time crystals. We also found that, unlike in many ordinary two-dimensional systems, small random changes do not destroy the order in our system. This allows the system to maintain a clear pattern even when such changes occur.'