Anisotropic Brownian diffusion near a nanostructured surface

The Brownian diffusion of sub-micrometer-sized particles (diameter 0.52 μm) in the vicinity of a nanostructured surface was experimentally characterized. The surface consisted of a repeating pattern of rectangular grooves with depth 35 nm and pitch 400 nm. It was found that the one-dimensional particle diffusivity parallel to the nanogrooves was significantly higher than the diffusivity perpendicular to the grooves ( 1.518 ± 0.274 (S.E.) μm 2/s compared to 0.704 ± 0.090 μm 2 / s ). No such anisotropy in the one-dimensional Brownian diffusivity was found for particles near a flat surface.