Cassie–Baxter state
= Cassie–Baxter state
{c}
{title2=$\cos\theta_*=f_s(1+\cos\theta_Y)-1$}
A <Cassie–Baxter state> is a composite wetting state in which a drop contacts solid asperities over area fraction $f_s$ and trapped gas over the remainder. An ideal area-weighted contact-angle model gives the displayed apparent angle from the smooth-solid <Young's equation> angle $\theta_Y$. Reducing solid contact can strongly enhance apparent <hydrophobicity>. Such a state can be metastable and can collapse when liquid enters the texture; roughness alone does not guarantee it.