Self-Assembled Binary Colloidal Crystals Under The Active Confinement

Colloidal crystal has the structure of colloidal particles in the orderly arrangement.To obtain functional materials based on the colloidal self-assembly,we can change properties of the colloidal particle or the environment properly.Especially in the optical field,colloidal crystal is an ideal material with eminent optical properties,which have attracted widespread attentions.In this research,we use a novel active confinement,in which the boundary is doing the periodic movement and the colloidal self-assembly is dynamic.Compared with traditional self-assembly,dynamic self-assembly requires continuous energy input,which leads the system far away from the equilibrium and may form the dynamic steady structure.This method can produce interesting structures that cannot be achieved by equilibrium self-assembly.In this work,we use Lammps to proceed molecular dynamics simulations to study the self-assembly of the mixture of opposite charged ellipsoidal colloidal particles and spherical colloidal particles under the active boundary with periodic oscillating.We find the emergence of mono-layer structure with the orientation of the ellipsoidal particles perpendicular to the boundary and the ordered distribution of confined particles.,Furthermore,the in-plane structure is tunable by changing the charge ratio between ellipsoids and spheres,including three different lattices(2, and 2).These structural transition can be explained by the minimal Madelung energy.Besides,when the distance between two boundaries and the number of particles is increased,we can observe the formation of multi-layer crystal structure.Next,we calculate the bound states in the continuum(BIC)of the binary quasi-two-dimensional colloidal crystal,indicating the unique optical property of such binary photonic crystal.Finally,we investigate the mixture of uncharged particles confined under the oscillating boundarycondition.The binary mixture system exhibits S phase where ellipsoidal particles are perpendicular to the boundary with the hierarchy structure,H phase where ellipsoidal particles are parallel to the boundary and L phase where the ellipsoidal particles are neither perpendicular nor parallel to the boundary.In these three phases,spherical particles all cluster together and display macroscopical phase separation.