  In this Letter we investigate the rupture instability of thin liquid films by
means of a bifurcation analysis in the vicinity of the short-scale instability
threshold. The rupture time estimate obtained in closed form as a function of
the relevant dimensionless groups is in striking agreement with the results of
the numerical simulations of the original nonlinear evolution equations. This
suggests that the weakly nonlinear theory captures the adequate physics of the
instability. When antagonistic (attractive/repulsive) molecular forces are
considered, nonlinear saturation of the instability becomes possible. We show
that the stability boundaries are determined by the van der Waals potential
alone.
