Wetting & Dewetting

Physics: Thin film equation: ∂h/∂t = ∇·[h³∇(γ∇²h − Π(h))]/(3μ), where Π(h) is the disjoining pressure. Spinodal dewetting occurs when ∂Π/∂h > 0 (film is linearly unstable). For van der Waals: Π = −A/(6πh³), giving instability for thin films. The dominant dewetting wavelength λ* ~ h²·√(γ/|∂²Π/∂h²|). Dewetting speed ~ (γ/μ)·θ³. Observed in polymer films (PS on Si): holes nucleate, expand, and rim instability breaks rim into droplets.