The Dynamic Behavior Of Vesicles In Obstacle System

Soft matter involves many research fields,such as physics,materials and biology.As a part of soft matter system,active system has been studied more and more widely in recent years.The biggest difference between active substances and inactive substances is that active substances can realize their own drive by consuming energy in the external environment,which is a spontaneous movement.Phase separation can occur in the active system,and unbalanced phenomena such as giant fluctuations can be observed.Since the 20th century,synthetic active particles have made a great breakthrough and can reach the nanometer scale.The active system has a wide application prospect,which can be used not only in pharmaceutical research,but also in environmental management.Although the research on active systems has made a breakthrough,it also faces many challenges.When the particles reach the nanometer level,we still have to continue to study its possibilities for life.We first introduce in detail the simulation methods used in this work,briefly explain the lammps software,and introduce in detail the three algorithms commonly used in the calculation process of lammps software.finally,we introduce the force field,periodic boundary and the essence of the nearest mirror method to be determined before simulation.The effect of the number of active particles inside flexible vesicles on the boundary of flexible vesicles was investigated.The modeling of flexible vesicles is realized by wrapping active particles in a polymer ring.By changing the number of active particles,the effect on the shape of the ring is studied,and the results are accurately ensured by multiple simulations and ensemble averaging.It is found that when the number of active particles increases,the circle moves closer to the circle.By changing the active position,adjusting the active force and the rotational diffusion coefficient of the active particles,it is concluded that the influence of the active particles and the passive particles on the ring is very different.When the rotational diffusion coefficient is small,the shape of the flexible vesicles fluctuates little with time.The aggregation behavior of vesicles around obstacles was studied.The concrete realization process is to place a circular obstacle in the two-dimensional plane and randomly place multiple vesicles around it,in which the vesicles can be deformed according to whether the outer boundary can be deformed into two categories:flexible vesicles and rigid vesicles.By adjusting the size of obstacles and the surface density of vesicles,the motion behavior of these two kinds of vesicles around obstacles is studied under different parameters.After many simulations,it is concluded that the aggregation of the two kinds of vesicles will occur around the obstacle.With the increase of vesicle density,the peak value of the maximum peak in the radial distribution image will decrease.The difference is that rigid vesicles have aggregation behavior in other parts of the system in addition to obvious aggregation around obstacles,while flexible vesicles have obvious aggregation around obstacles.There is no self-aggregation elsewhere in the system,because the boundary of flexible vesicles can be deformed,which makes vesicle aggregation unstable and difficult to cluster.With the increase of vesicle surface density,the Gini number decreases gradually,and the Gini number of rigid vesicles is lower under the same parameters.Finally,the conclusion of this simulation work is summarized,and the follow-up work is prospected.