Time-modulated Chiral Solids*

The shape of passive solids and liquids is typically determined by the time-independent interactions between thermally fluctuating constituents. 

By contrast, in active and driven materials, the interactions can be modulated in time opening a new design axis. 

Using an external field, we drive magnetic colloids to rotate with a rotational frequency that is modulated in time, generating non-trivial structure. 

We show how the structures we observe are created as a result of time modulated bulk stresses and orientationally dependent surface forces.