We studied the diffusion of ellipsoidal colloids by using a combination of single-particle tracking (SPT) and differential dynamic microscopy (DDM). The micrometer-sized polystyrene particles have an aspect ratio of ≈ 4.3. SPT provides the particle trajectories and translation diffusion coefficient of the particles. DDM analyses appropriate for anisotropic particles were then used to extract the rotational diffusion coefficient of the particles. The results matched well with the theoretical prediction of translational and rotational diffusion coefficients for ellipsoids in the bulk. We extended our method to surface bound particles, which shows that rotation slowed by a larger amount compared to translation. This can be explained qualitatively by assuming heterogeneity of viscous and hydrodynamic forces experienced by surface bound particles. The research will be useful to study the viscous friction experienced by anisotropic colloids in complex fluids and surface friction at chemically or topologically modified substrates.

我们通过使用单粒子跟踪 (SPT) 和差分动态显微镜 (DDM) 的组合研究了椭球胶体的扩散。微米级聚苯乙烯颗粒的纵横比约为 4.3。SPT 提供粒子的粒子轨迹和平移扩散系数。然后使用适用于各向异性粒子的 DDM 分析来提取粒子的旋转扩散系数。结果与体中椭球的平移和旋转扩散系数的理论预测非常吻合。我们将我们的方法扩展到表面束缚粒子，这表明与平移相比，旋转减慢了更大的数量。这可以通过假设表面结合颗粒所经历的粘性力和流体动力的异质性来定性地解释。