Control of emergent states in active colloids through memory, activity modulations, and confinement

The spontaneous emergence of correlated states is a prime example of complex collective dynamics and self-organization observed in active matter. Many active synthetic systems are realized by ensembles of externally energized particles. In this talk I will demonstrate a plethora of unexpected and complex collective phenomena revealed in active liquids formed by rolling colloids experimentally realized by either Quincke or magnetic rollers spontaneously selecting the direction of motion.

I will show how the emergent multi-vortical states in concentrated magnetic roller liquids could be transformed into globally correlated antiferromagnetically ordered lattices of vortices with the help of a soft confinement, and how the polar states of each vortex in both sublattices can be simultaneously flipped by certain activity modulations utilizing the information stored in the ensemble. I will further demonstrate that temporal modulation of activity is an effective tool to induce complex collective response and non-trivial self-organization in active roller liquids often not accessible under continuous energy input (such as dynamic lattices and spontaneous activity shock-waves). On the example of a global polar state formed by Quincke rollers, that active liquids formed by motile particles are capable of preserving their dynamic state information in seemingly random dynamic arrangements of the particles forming a collective dynamic “memory” of the ensemble. The stored information can be accessed and exploited to systematically command subsequent globally correlated polar states of the active liquid through temporal control of the activity.