Contact angles of sessile droplets deposited on rough and flat surfaces in the presence of external fields

The paper proposes a general framework allowing the analysis of wetting problems in the situation when interfacial tensions depend on external fields. An equation predicting apparent contact angles of sessile droplets deposited on rough surfaces in the presence of external fields is derived. The problem of wetting is discussed in the framework of the variational approach. Derivation of a general equation generalizing the Cassie and Wenzel approaches is presented. The effects related to the line tension which are important for nano-structured surfaces are considered.