Test of the diffusing-diffusivity mechanism using near-wall colloidal dynamics

Abstract

The mechanism of diffusing diffusivity predicts that, in environments where the diffusivity changes gradually, the displacement distribution becomes non-Gaussian, even though the mean-squared displacement (MSD) grows linearly with time. Here, we report single-particle tracking measurements of the diffusion of colloidal spheres near a planar substrate. Because the local effective diffusivity is known, we have been able to carry out the first direct test of this mechanism for diffusion in inhomogeneous media.

13 pages, 12 figures (including supplement. Portions of this work previously appeared as arXiv:1602.07644, which was subsequently withdrawn. This version adds a new author and presents new data and analysis. Main conclusions in both papers are the same