, where rs = r s /l c and R = R/l c are nondimensionalized by the capillary length l c = ! γ/ρg = 2.7 mm, where γ and ρ are water's surface tension and density, while g is gravitational acceleration. For large droplets R ≫ l c , the droplet's weight dominate over the capillary adhesion force (second term in Equation 1 can be ignored); whereas for small droplets with R ≪ l c , capillarity effects dominate (first term can be ignored). Hence, Equation 1 simplifies to