The focus of the present study is on the contact angle θ that the interface between two phases ('1' and '2') forms at the three-phase contact line on a solid substrate ('s') which is locally flat (Fig. ). * Given the interfacial tension between the two phases of interest, γ 12 , and the surface energies of the two phases against the substrate, γ s1 and γ s2 , the contact angle satisfies the Young equation, γ s1 = γ s2 + γ 12 cos θ .