Anisotropic Dynamics of Binary Particles in Confined Geometries

The diffusion dynamics of colloidal particles in a good solvent confined between two parallel quartz walls have been studied within the framework of dynamical density functional theory. The highly ordered density layers induced by interfacial effects give rise to the oscillating dynamics, resulting in position-dependent structural relaxations and diffusivities. Further investigation reveals that particle size, particle-wall interaction, and slitpore width play different roles in affecting the oscillating behaviors along different directions. As a result, the theory yields the local mean square displacements in perpendicular and parallel directions, which agree remarkably well with prior experimental measurements. The results indicate that the mean square displacements can be quantitatively predicted based on the knowledge of inhomogeneous thermodynamics and dynamics. The local and averaged free energy evolution of the binary particles has been described and presented to understand their dynamic mechanism in confined geometry.