Activity-Driven Dewetting and Rupture in Thin Liquid Films

Abstract

Thin-film dewetting is classically governed by an adhesion-mediated spinodal instability in which curvature-driven diffusion controls post-rupture coarsening. We show that internal activity fundamentally restructures this instability. Using a minimal microscopic model of an active liquid film on a solid substrate, we identify a competition between active stresses and film-substrate adhesion that produces two independently regulated dynamical length scales: vertical liquid accumulation and lateral rupture propagation. While passive films exhibit universal diffusion-limited growth, $\ell_z(t)\sim t^{1/3}$, activity converts transport from curvature-controlled diffusion to persistence-driven motion, yielding a continuous increase of the coarsening exponent from $\approx 0.33$ to $\approx 0.6$. The growth law analysis shows that persistent self-propulsion introduces an advective flux that competes with curvature-induced chemical potential gradients, enhancing growth when the persistence length becomes comparable to the evolving domain size. Simultaneously, the rupture front transitions from dissipative spreading to strongly accelerated propagation approaching ballistic scaling. This decoupling shows that activity does not simply renormalize effective surface forces but generates a distinct nonequilibrium interfacial instability governed by the balance between persistence length and adhesion. The results provide a minimal physical mechanism linking classical thin-film dewetting to dewetting-like rupture observed in active and biological materials.

Figures (10)

• Figure 1: Growth dynamics in passive films. (a) Vertical domain size $\ell_z(t)$ showing diffusion-limited growth $\sim t^{1/3}$. (b) Lateral rupture extent $\ell_{xy}(t)$. Both observables originate from spinodal rupture, with diffusion-limited vertical growth and friction-limited contact line motion.
• Figure 2: Side view of an active thin film undergoing dewetting for activity $f_A=1$ and film-substrate interaction $\epsilon_{WA}=0.5$. Red particles denote the substrate and blue particles the active fluid. The film develops protrusive structures and partial detachment from the substrate, indicating that active stresses compete with adhesion.
• Figure 3: Vertical liquid accumulation length $\ell_z(t)$ for different activity strengths and film-substrate interactions. The growth exponent increases continuously from diffusion-limited behavior ($\alpha\approx1/3$) at strong adhesion to enhanced growth ($\alpha\approx0.6$) at weak adhesion and high activity. Dashed lines indicate power-law guides to the eye.
• Figure 4: Growth exponent $\alpha$ as a function of activity strength $f_A$ and film-substrate interaction $\epsilon_{WA}$. The crossover from diffusion-dominated to activity-dominated growth is controlled by the competition between persistence and adhesion.
• Figure 5: Lateral rupture propagation length $\ell_{xy}(t)$. (a) Dependence on activity at fixed interaction. (b) Dependence on interaction at fixed activity. High activity under weak adhesion produces strongly accelerated spreading of the rupture front.