Activity-induced interactions and self-assembly in model active matter

Flocks of birds, schools of fishes, or bacterial colonies constitute examples of living systems that coordinate their motion. In all these systems their constituent elements generate motion due to energy consumption and can exchange information or react sensitively to chemical cues in order to move together or to react collectively to external signals. Artificial systems, such as Janus colloids, exploit the  heterogeneous compositions of their surface to displace  as a result of the heterogeneous chemical processes that take place in the presence of appropriate chemical substances. 

All these systems are intrinsically out of equilibrium in the absence of any external driving. Therefore, their  collective behavior emerges  from a balance between their direct interactions and the indirect coupling to the medium in which they move, and a self-consistent  dynamical approach is required to analyze their evolution. The mechanical balance that determines their collective behavior  makes these systems very versatile.  

Synthetic  active particles constitute a class of model systems with huge technological potential. I will analyze in the role that phoresis plays in the rectification of  such model systems and  the different mechanisms that lead to their propulsion. I will discuss the role that the dynamics of the embedding medium plays in the different regimes that characterize  active colloids. These simple  models will help to address the fundamental properties of active systems  and I will discuss the generic  implications that self-propulsion has in the emergence of structures in suspensions of model self-propelled particles.  

In general, the  steady states that characterizes these systems require a consistent dynamic treatment. I will analyze the role that the medium in which active colloids displace has in generating correlations among active particles them.  

I will  consider different mechanisms, such as swimming or heterogeneous catalysis,  which lead to spontaneous self-organization in the absence of external driving for a variety of  active suspensions. Such a  comparison will help to discern between specific ingredients and general features determining the emergent properties of active systems.  

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