Non-universal dynamic exponents for thin-film spreading

One of the manifestations of thin-film spreading is the phenomenon of a precursor spreading in front of an advancing droplet. The microscopic characteristics of the precursor dynamics is still not fully understood. In this letter we study top-view thin-film spreading using a driven lattice gas model of two layers, representing the bulk and the precursor film, first suggested by Abraham et al. By changing the relations between the Hamaker constant (van der Waals interaction), the nearest-neighbor interaction (surface tension) and the temperature, we studied the effects of these parameters on the scaling exponents describing the spreading of both layers. We found that the scaling exponents of both layers are not universal, and show that they strongly depend on these parameters. We also discuss the relation between our results and well-known laws for the bulk dynamics of spreading droplets, such as the Tanner and Lopez laws, as well as with recent results on precursor dynamics.