Spreading fronts of wetting liquid droplets: Microscopic simulations and universal fluctuations

We have used kinetic Monte Carlo (kMC) simulations of a lattice gas to study front fluctuations in the spreading of a nonvolatile liquid droplet onto a solid substrate. Our results are consistent with a diffusive growth law for the radius of the precursor layer, R ??? t8, with 8 ??? 1/2 in all the conditions considered for temperature and substrate wettability, in good agreement with previous studies. The fluctuations of the front exhibit kinetic roughening properties with exponent values which depend on temperature T, but become T independent for sufficiently high T. Moreover, strong evidence of intrinsic anomalous scaling has been found, characterized by different values of the roughness exponent at short and large length scales. Although such a behavior differs from the scaling properties of the one-dimensional Kardar-Parisi-Zhang (KPZ) universality class, the front covariance and the probability distribution function of front fluctuations found in our kMC simulations do display KPZ behavior, agreeing with simulations of a continuum height equation proposed in this context. However, this equation does not feature intrinsic anomalous scaling, at variance with the discrete model.

Automated summary

This study uses kinetic Monte Carlo simulations to investigate front fluctuations in the spreading of a nonvolatile liquid droplet on a solid substrate. The results show that the diffusion growth of the precursor layer follows a power law with an exponent of 1/2, in agreement with previous studies. The front fluctuations exhibit kinetic roughening properties that depend on temperature, but become temperature independent at higher temperatures. Additionally, evidence of intrinsic anomalous scaling is found, with different roughness exponents at different length scales.