You can get the concept of: Double membrane, surface tension, conductivity of electrolytes.
Principle: If a platinum ring from a thin wire to extend through the aqueous solution on its surface, forming a tubular film, the boundaries of which (with sotorony atmosphere) is a membrane. The film is an aqueous solution of lauryl sulfate ions sandwiched between two monomolecular membranes. Its thickness can be estimated by measuring the conductivity, provided that the conductivity of the electrolyte and the geometry of the film are known.
