Langmuir • Vol 39 • No 31
Cassie’s Law Reformulated: Composite Surfaces from Superspreading to Superhydrophobic
July 2023 • Glen McHale, Rodrigo Ledesma‐Aguilar, Chiara Neto
In 1948, Cassie provided an equation describing the wetting of a smooth, heterogeneous surface. He proposed that the cosine of the contact angle, θ<sub>c</sub>, for a droplet on a composite surface could be predicted from a weighted average using the fractional surface areas, <i>f</i><sub><i>i</i></sub>, of the cosines of contact angles of a droplet on the individual component surfaces, i.e., cos θ<sub>c</sub> = <i>f</i><sub>1</sub> cos θ<sub>1</sub> + <i>f</i><sub>2</sub> cos θ<sub>2</sub>. This was a generalizat…