Simultaneous determination of surface energy and roughness of dense membranes by a modified contact angle method

•Membrane surface energy and roughness are solved in one step from contact angles.•The theoretical foundation is the combined Young–Dupré and Wenzel equations.•Solved surface energy includes Lifshitz–van der Waals and Lewis acid/base components.•Solved surface roughness (surface area difference) is comparable with AFM results.•Higher roughness and hydrophilicity cause larger deviation of energy determination.