Abstract: A hydrophobic biofilm membrane modified with a spiropolyurethane may be used for desalination of salt water to fresh water. The spiropolyurethane component of the membrane can produce a hydrophobic spin membrane boundary which attracts saline water, and where the hydrophobic spin membrane boundary can comprise a hinge-like motion for capture of salt molecules via a loose pore-gate spongy membrane surface texture while allowing desalinated water to flow through the porous membrane. The membrane is useful in both reverse osmosis (RO) and membrane distillation (MD) separations, including the desalination.