Wetting Transition

Contact angle, Young equation, spreading coefficient

θ = 90° | S = 0.00 | Partial wetting

Drop cross-section on substrate

Contact angle vs surface energies

γ_SV (solid-vapor): 0.50

γ_SL (solid-liquid): 0.20

γ_LV (liq-vapor): 0.40

Young equation: γ_SV = γ_SL + γ_LV cos θ → cos θ = (γ_SV − γ_SL)/γ_LV
Spreading coefficient: S = γ_SV − γ_SL − γ_LV
S > 0: complete wetting (θ→0). S < 0: partial wetting. Wetting transition: S crosses 0.