Dynamic Behavior Of Self-propelled Particles Under Boundary Or Topological Constraints

Active matter is a hot frontier of soft matter physics.Because of typical non-equilibrium characteristics,active systems exhibit rich dynamic behaviors.Currently,the dynamics of active agents under confinement has been studied extensively in microscopic experiments and simulations,but the macroscopic experiments are scarce.Recently,it has been found that the geometric asymmetry of the Brownian ratchet in the bath of active particles can spontaneously generate directional rotation.And researchers are paying more and more attention to active wormlike chains.Filaments can exhibit different patterns under different chain stiffness and driving force.In this thesis,the directional rotation of the symmetrical ratchet and active granular chains were studied by granular experiments and numerical simulations.First,the geometrically symmetrical ratchet in the active Brown particle bath is studied in detail through a combination of experiments and numerical simulations.It was found that geometrically symmetrical ratchets in a simple circular active particle bath can produce long-lasting directional rotation under conditions of high particle areocular density and small rotation diffusion coefficients.Dynamic spontaneous symmetry breaking is its intrinsic physical mechanism.In addition,through the corresponding simulation studies,it was also found that the volume repulsion and spatial accumulation effect between active Brown particles did not strengthen the directional rotation of the geometric symmetrical ratchet.Secondly,the difference in the dynamic behavior of the self-driven particle chain under the action of noise and chain stiffness was studied.It is found that the dynamic behavior of the self-driven particle chain is greatly correlated with the chain rigidity and noise.Under different parameter conditions,the self-driven particle chain will present four states:spiral state,one-way transport dynamic,steering state and oscillation state.In general,with the increase of chain stiffness and noise,the active particle chain will undergo a transition process from spiral state to steering state to oscillation state,and unidirectional continuous motion occurs in the case of translation or rotational diffusion coefficient is small,and the stiffness is large.In addition,the rotational diffusion coefficient can induce the linear synchronous movement of the particle chain,while the translational diffusion coefficient induces the lateral synchronous movement of the particle chain.The results of this paper have important guiding significance for the kinetic study of active systems induced by geometric constraints.