On the Dynamics of Spin-Coating of Rapidly Dried Colloidal Suspensions*

The dynamics during the spin-coating of rapidly dried colloidal suspensions was studied. High-speed photography of the temporal evolution of long-range orientational order in both the fluid and dried phases shows three distinct symmetry transitions. Radial non-uniformity in the thickness of the spun suspension was measured from interference fringes, and from this the thinning rates as a function of radial position and time were calculated. A transition between two regimes is observed in the drying front speed. This transition is correlated with changes in the long-range orientational order (dried structure) as well as in the thickness profiles (in the fluid and dried structures).