Dynamic characteristics of droplet impingement on microscale hole-patterned surfaces with anodization

This study aims to experimentally examine the dynamic characteristics of a liquid droplet impinging on the microscale hole-patterned surfaces with the anodization method to make the hydrophilic hole-patterned surface. We studied static and dynamic wetting behavior and compared the hydrophobic characteristics of a drilled hole-patterned surface. The equilibrium contact angle, the dynamic contact diameter, and the dynamic contact angle are measured over time by using image analysis. By modeling the force balance between capillary and hydrostatic forces, the liquid displacement length and equilibrium contact angle of the anodized bare surfaces is estimated and compared with experimental data. It is found that the dynamic contact angle decreased with an increase in the hole area fraction for the anodized hole-patterned surface. In contrast, the equilibrium contact angle and the dynamic contact angle in the hole-patterned surface without the anodization increased with the hole area fraction, showing different tendencies. It is also shown that the dynamic contact diameter increased more on the area fraction and Weber number on the hole-patterned surfaces with the anodization.