Minimum dimensionless pressure technique for the indirect measurement of contact angles on super-hydrophobic surfaces

Measuring contact angles (CAs) on super-hydrophobic surfaces (CA ≥150°) can be challenging using traditional methods. In this work, we develop an alternative technique to measure CAs indirectly by measuring the minimum of the dimensionless hydrostatic pressure of a droplet as it de-wets a surface. This technique does not require measuring the slope of the profile close to the three-phase contact line and is devoid of any external pressure or force gauges. An experimental proof of principle is presented. Our results suggest that this technique may become a viable alternative for measuring the CA on super-hydrophobic and liquid repellent surfaces with relatively low uncertainty.