Self-assembly Behavior Of Active Colloidal Particles

Self-assembly is an important tool and method to create new materials by nature.The self-assembly of equilibrium states can be predicted by the minimum free energy of system.However,self-assembly usually is dynamic and non-equilibrium in nature.Through energy input and output,the non-equilibrium system can lead to lots of complex structures.This thesis focuses on the self-assembly behavior of colloidal particles in active system using molecular dynamics simulations.Firstly,we investigate the influence of temperature and active force on dynamic selfassembly of self-propelling “+” shape.It was found that the system undergoes a transition from a homogeneous gas phase to stable solid-gas coexistence phase with the increase of self-propelling force or the decrease of temperature.There also exists an interesting intermediate phase,named the metastable solid-gas coexistence phase.The proportion of dense-phase square crystal regions is higher and the particles is more ordered in the metastable phase.Due to the specific shape of building block,the dense-phase structure is more stable and long living in the steady state.Additionally,it was also found that the coarsening size of cluster is approximately 1/3.Secondly,we study the self-assembly of long rod in active particle baths.We find that the cluster size of self-assembly is inversely proportional to the propelling force of active particles,and is proportional to the concentration of active particles.Furthermore,it was found that the propelling force is a key factor for cluster stability.Moreover,in the mixed system,the passive long rod system also exhibits the density fluctuations and diffusion behaviors similar to the active rod system,implying that the passive rods in the active environment have the similar features of active rods.