Characterization of the mechanical properties of a water/oil/water multiple emulsion oily membrane by a micropipette aspiration technique

The main goal of this paper was to apply to water/oil/water (w/o/w) multiple emulsions the micropipette aspiration method, which is known as one of the most adopted techniques to study globule or cell deformability. It consists in aspirating, step by step, an individual oily globule into a cylindrical glass tube under well-controlled conditions of aspiration. This method provides some physical parameters of the oily membrane. This micromanipulation technique was applied to various multiple emulsion formulations in order to evaluate both the elastic properties and the interfacial tension of the oily membrane as a function of the lipophilic surfactant concentration. It was shown that the elastic shear modulus and the interfacial tension of the oily membrane increased with the lipophilic surfactant concentration. The analysis of the behavior of the multiple emulsion during a swelling-breakdown and release kinetics confirmed these results. This rigidification of the membrane could be produced during the second step of the preparation of the multiple emulsion, by a migration of the lipophilic surfactant to the interface between the oily and the external aqueous phases. (C) 1999 Elsevier Science B.V. All rights reserved.