Self-diffusion of rod-like viruses in the nematic phase

Abstract

We measure the self-diffusion of colloidal rod-like virus {\it 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 ($D_{\parallel }$) and perpendicular ($D_{\perp }$) to the nematic director is measured. The ratio ($D_{\parallel }/D_{\perp }$) increases monotonically with increasing virus concentration. Crossing the isotropic-nematic phase boundary results in increase of $D_{\parallel }$ and decrease of $D_{\perp }$ when compared to the diffusion in the isotropic phase ($D_{iso}$).

7 pages, 4 figures, to appear in Europhysics Letters