Water/oil/water thin films: construction and applications

With the classical “thin-film balance” apparatus, one can study the properties of thin soap films (air/water/air films). Here, we present a new version of that apparatus allowing us to build a single thin oil film horizontally held on a frame and completely immersed in water. The frame used here is a glass frit: to make it suitable for holding oil films in water and to overcome wetting problems, we have developed a special surface treatment by silanization of the frit. With that device, we can directly and simultaneously control, change and measure both the film thickness and the disjoining pressure in these water/oil/water films. Related to structural, dynamical and stability issues, the range of studies and applications is wide with the new experimental configuration. We present experimental tests on the validity of the setup, also showing typical thickness instabilities which appears to be important in these kind of films. We also discuss information provided on the stability of thin liquid films in liquid-liquid extraction problems.