Water Contact Angle for Heterogeneous Surface
The measured contact angle is calculated for a rough, heterogeneous surface using the Wenzei and Cassie laws. The contact surface is a mixture of materials A and B. With sliders, you can change the fraction of component A and the surface contact angles of each material (θA and θB). Also, a slider can change the surface roughness; for a completely smooth surface, the surface roughness ratio used in the Wenzei equation is 1. The measured contact angle (θW) is calculated and displayed above the water droplet graphic; arrows on the plot show where θW is measured. Surfaces with water contact angles θW > 90° have low wettability and are considered hydrophobic, whereas θW < 90° means the surface has high wettability and is considered hydrophilic. When θW = 0°, complete wetting occurs.

Download the CDF file to view the simulation using the free Wolfram CDF player.