Perspectives: Synthetic Bilayer Membrane and Giant Nanomembrane.

This is a short story of the beginning of our research on bilayer assembly and its subsequent developments. Inspired by the fluid mosaic model of the cell membrane, we started in the mid 1970's to look for the synthetic counterpart of membrane-forming biolipids. It was soon found by electron microscopy that the stable molecular bilayer was formed from double-chain ammonium amphiphiles. This finding was extended to a number of related types of compounds, thus establishing that the bilayer formation itself was general physicochemical phenomena. The same concept was applicable to non-aqueous systems. The molecular scale thickness-one of the unique features of the biological membrane-was partially reproduced by development of giant nanomembranes. Finally, prospects and some unsolved problems are discussed.