Evaluation of surface wettability by means of the measurement of the adhesive force between a microstructured hydrophobic surface and a water droplet

Abstract

The pull-off forces between water and microstructured hydrophobic surfaces were calculated and measured in this study. A hydrophilically modified nickel disk was used to hold a drop of water. Regardless of the type of surface structure, as the solid fraction decreased, the pull-off force gradually decreased. Surfaces with pillar type structures had similar pull-off forces with different pillar sizes when the solid fractions were identical. This indicates that pillar size had no significant effect on the pull-off force. The pull-off force measured from the pore structures was higher than that measured from the pillar structures. As a result, the pillar-type microstructure provides a surface with a lower surface adhesive force than the pore type. The measurement technique used in this study allows the surface adhesive force to be quantified, making it very useful tool for evaluating the wettability of a solid surface.