Diffusion in complex fluids

Self-Diffusion of Rods

Dispersions of colloidal viruses, in our case fd virus, display a cascade of phase transitions, from isotropic to the nematic [Lettinga2005], the smectic [Lettinga2007Pouget2011] and the columnar [Naderi2013] phase with increasing concentration. Uncovering the dynamics underlying these phase transitions, which is fundamental to understand the process of self-assembly, as it is purely driven by entropy. We use fluorescence video microscopy in order to study the self-diffusion of rods in the different phases. This study gave and still gives a wealth of surprising features, such as discretised Brownian diffusion in the smectic and large rods that diffuse faster than short rods.

Two viruses with different lengths, and with different fluorescent labeling, diffusing in a smectic phase of native fd-virus.