Dynamical and structural insights into the smectic phase of rod-like particles

Self-diffusion in a model system of rod-like particles is studied in the smectic (or lamellar) phase. The experimental system is formed by a colloidal suspension of filamentous fd virus particles, which allows the direct visualization at the scale of the single particle of mass transport between the smectic layers. Self-diffusion takes place preferentially in the direction normal to the smectic layers and occurs in steps of one rod length, reminiscent of a hopping-type of transport. The probability density function is obtained experimentally at different times and is found to be in qualitative agreement with theoretical predictions based on a dynamical density functional theory.