Disclosed are novel water membranes comprising lipid bilayers incorporating functional aqua-porins. The lipid bilayers are arranged in sandwich structures including hydrophilic or hydro-phobic support materials. Also disclosed are water purification devices/systems, including reverse osmosis filtering devices that include membranes having functional aquaporins. Methods of water purification and methods of preparing the membranes are also disclosed. Further, the invention provides for a new type of perforated, hydrophobic polymer film and to membranes containing lipid bilayers having other transmembrane proteins than aquaporins introduced.