Spreading of droplets impacting different wettable surfaces at a Weber number close to zero

Abstract Six different surfaces ranging from superhydrophilic to superhydrophobic were fabricated. Droplet impact experiments were conducted on these surfaces with water droplets 2.25 mm in diameter at a Weber number close to zero to study the effects of surface wettability on the impact process and post-impact oscillation. Droplet impact on all surfaces, except for superhydrophobic surfaces, is dominated by a spreading stage and no evident retraction is observed. Using the inertia-capillarity time tc = ρ R 0 3 / σ as characteristic time, the spreading stage on all surfaces at We