a portion of the cell membrane consisting of phospholipids with their nonpolar tails in the interior and their polar heads interfacing with the polar water molecules

See phospholipid bilayer.

bimolecular film

One layer of nickel and one layer of aluminum in a NanoFoil®. It is convenient to discuss the size or scale of the NanoFoil® microstructure in terms of bilayers, since the ratio of aluminum layer thickness to nickel layer thickness is constant but the actual thicknesses are varied.