Abstract
We measure the self-diffusion of colloidal rod-like virus fd in an isotropic and nematic phase. A low-volume fraction of viruses are labelled with a fluorescent dye and dissolved in a background of unlabelled rods. The trajectories of individual rods are visualized using fluorescence microscopy from which the diffusion constant is extracted. The diffusion parallel (D∥) and perpendicular (D⊥) to the nematic director is measured. The ratio (D∥/D⊥) increases monotonically with increasing virus concentration. Crossing the isotropic-nematic phase boundary results in increase of D∥ and decrease of D⊥ when compared to the diffusion in the isotropic phase (Diso).