ABSTRACT
This chapter considers the properties of flexible interfaces or membranes. It focuses on fluid membranes, which are important in industrial applications such as encapsulation and cleaning. Although fluid membranes can be composed of many different types of chemical and molecular species, their behavior can be understood from a unified point of view that considers the free energy of deformation of the membrane. The chapter also considers a fluid, monolayer, membrane at a water-oil interface in equilibrium with a dilute solution of amphiphiles in the water and oil. Surfactant molecules or amphiphiles consist of molecules that combine both polar and nonpolar parts. The thickness of the membrane can be found by requiring that the curvature energy include only pure curvature deformations — that there be no overall compression or expansion of the membrane. At length scales of order the persistence length, the curvature energy competes with the entropy of the membrane conformations.
