DYNAMICS OF WETTING WITH A DISORDERED SUBSTRATE - THE CONTACT-ANGLE HYSTERESIS

The edge of an advancing or receding two-dimensional sessile drop is studied using Monte Carlo dynamics and analytical arguments. It is found that for disordered substrates an advancing angle theta(a) or a receding angle theta(r), both different from the equilibrium angle, appear and remain stable during a lifetime much larger than the time needed to reach equilibrium with a pure substrate. Much larger means a ratio tending to infinity in the thermodynamic limit.