Hi Mems people!

I'm studying surface roughness correlated to wettability.
I've found difficulties in calculating Wenzel's roughness r and the fraction of
solid surface in contact with liquid, in cassie's equation, having a random
rough surface,(as with geometrical surfaces I can use Patankar's derivations).
Can anyone help me?

Also does anyone have an idea how to calculate the height–height and lateral
correlation function of random surfaces, using AFM?

thanks