The Two Classic Wetting Models

Since one of the components (f- is air, cosl80°=-l, Eq. (4.3) becomes the famous Cassie-Baxter equation  

Experimentally, a small droplet of water was dispensed to the center of the textured area. The diameter of the contact area D was recorded and the advancing/receding contact angles Oa Or were determined. Small amount of water was added next. The diameter of the expanded drop and Oa/Or of the drop were determined. This procedure is repeated for other samples, and the data are summarized in Table 4.1. 

---