inspired by the bioadhesion principle, composite membranes with ultrathin, defect-free skin layer (about 10-90 nm) were fabricated by simply dipping the porous hollow fiber support layer into an aqueous alkaline dopamine solution. The thickness and compactness of the skin layer were conveniently tuned by varying dipping conditions (dopamine concentration, soaking time, and pH values). The as-prepared membranes displayed strong interfacial binding strength, well-defined free volume characteristics, and consequently superior dehumidification performance. The dehumidification experiments using water vapor/propylene as model showed that the water permeance and separation factor were 9316.7 GPU and infinite for the composite membranes fabricated at the dopamine concentration 2 mg ml(-1) and the pH 9.4. (C) 2009 Elsevier B.V. All rights reserved.