Europhys. Lett.
Volume 71, Number 4, August 2005
Page(s) 692 - 698
Section Interdisciplinary physics and related areas of science and technology
Published online 22 July 2005
Europhys. Lett., 71 (4), pp. 692-698 (2005)
DOI: 10.1209/epl/i2005-10127-x

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

M. P. Lettinga1, E. Barry2 and Z. Dogic2

1  IFF, Institut Weiche Materie, Forschungszentrum Jülich - D-52425 Jülich, Germany
2  Rowland Institute at Harvard, Harvard University - Cambridge, MA 02142, USA

received 21 March 2005; accepted 17 June 2005
published online 22 July 2005

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 ( $D_{\parallel}$) 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 ( $D_{\ab{iso}}$).

82.70.-y - Disperse systems; complex fluids.
61.30.-v - Liquid crystals.
66.10.-x - Diffusion and ionic conduction in liquids.

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