Chiral Active Matter

Self-organizing, Self-healing Material of Magnetic Spinners

Smart and active materials can adapt their properties spontaneously in response to changing environmental conditions; these dynamically controllable properties have already led to a wide range of applications. For example, shock absorbers containing magnetorheological fluids are able to adapt their dampening properties.  

We have developed and studied a new, active system of magnetic microparticles moving at an air-water interface. The particles are set into spinning motion by a magnetic field rotating in the plane of the water surface.

The system self-organizes in a non-equilibrium steady state. Depending on the frequency of the magnetic field, the particles cluster together to form shorter or longer rotating chains. Furthermore, the chains arrange themselves spontaneously and dynamically at the interface in a crystal-like structure. After a disturbance, e.g. by dropping a larger particle into their arrangement, the order is rapidly restored in a self-healing process.

Also, the system has tuneable transport properties. Non-magnetic particles can be actively transported through the system and that this transport can be controlled externally through the field frequency.

Reference: K. Han, G. Kokot, S. Das, R. G. Winkler, G. Gompper, A. Snezhko; Reconfigurable structure and tunable transport in synchronized active spinner materials; Science Advances 6, eaaz8535 (2020)