Matéria Ativa em substratos decorados

Abstract

The objective of this Thesis is to study the behavior of Active Matter in standardized substrates and to understand how the controlled geometry of the environment can influence the dynamic behavior of these systems. More specifically, we want to describe under which conditions we can modify or induce collective behavior in order to obtain particle transport. In our approach, we treat Active Matter as a set of Self-Propelled Particles. We also consider a model in which the particles are Active Bars. We present an overview of the subject, paying attention to the main models and most expressive works on the subject. We present in detail the fundamental models used to study active systems, such as, for example, the Vicsek model, and an approach based on a Langevin-type equation. We present our results based on a systematic study of a two-dimensional system of active particles in the presence of rigid asymmetric obstacles (semicircular). The transport of particles in the system is induced locally by asymmetric obstacles and as a consequence of the interaction between active particles and obstacles. Despite the erratic movement of each particle, the collective behavior outweighs the individual, resulting in an effective movement along a preferential direction, characterized by the average velocity of the particles different from zero. We study the current of particles and active bars in terms of separation between obstacles, size of obstacles, intensity of noise that defines the erratic movement of particles and the fraction of occupancy. We also studied the probability of clot formation (hyper agglomeration and capture structures), a phenomenon that was observed in the active bar system. Finally, we present the results of the effects of unordered arrangement of obstacles on the transport of the system of particles and active bars and how the diffusion is modified when the number of obstacles is changed, removing them randomly from the ordered network.