Apparatus for plasma surface treating and preparation of membrane layers

An apparatus suitable for plasma surface treating (e.g., forming a membrane layer on a substrate surface) comprises a plasma generation section which is operable at least at substantially atmospheric pressure and is in communication via at least one plasma inlet (e.g., a nozzle) with an enclosed plasma treating section which is operable at a lower pressure than the plasma generation section, and wherein the plasma treating-section is in communication with an inlet for a fluid (e.g., polymerizable) reactant used to form a layer on the substrate surface.