Scheludko cell

Fig. 3.13. Sketch of an axisymmetric liquid film in a "Scheludko cell" a - glass ring of diameter 2R, b - surfactant solution, c - thin film of diameter 2Tq, d - tube for the sucking off of the liquid of a relatively thick film...

Figure 21.4. Cross-sectional view of typical film-holders used in the thin-film balance (a) Scheludko cell (b) porous disc holder (from ref (11))...

FIGURE 1.6 Axisymmetric drainage of foam film with immobile air-water surfaces, (a) Dimple and barrier ring that form, (b) Defining maximum dimple size where barrier ring is absent and where film is formed in a cylindrical Scheludko cell (references [13,39] see Section 2.3.1). Radius of curvature, of Plateau border air-water surface is approximated by radius, R, of cell—is radius of curvature of air-water surface of the dimple. (Reprinted with permission from Joye, J. et al., Langmuir, 8, 3083. Copyright 1992 American Chemical Society.)... 

The so-called Scheludko cell has found wide application in studies of foam films. This cell was first proposed by Scheludko and Exerowa [35, 36] more than half a century ago. It consists of a (usually) glass cylinder containing a biconcave drop of surfactant solution. A tube inserted into the side of the cylinder permits control of... 

FIGURE 2.8 Typical setup for observation of antifoam drops in foam film using a Scheludko cell. (From Scheludko, A., Exerowa, D., Commun. Dept. Chem. Bulg. Acad. Sci., 7, 123, 1959 Scheludko, A.,Adv. Colloid Interface Sci., 1, 391, 1967.)... 

Observation of the drainage of foam films containing drops of these alcohols using a Scheludko cell revealed that the oil drops were swept out of the films without causing film rupture. Indeed, the drainage behavior and stability of the films were apparently totally unaffected by the presence of the oils despite a reduction in equilibrium surface tension. Arnaudov et al. [7] then concluded that these alcohols must cause foam collapse by rupturing Plateau borders rather than foam films as described in Section 4.5.3. 

Careful loading of the Scheludko cell to avoid contamination of the air-water surface with a prespread layer of oil surprisingly eliminated the formation of unstable bridges and the accompanying foam film instability. Denkov et al. [54] attributed this observation to the effect of the spread layer on the emergence of the PDMS oil into the air-water snrface, which they have later shown to augment the effect of the hydrophobed silica. We return to this issue in Section 4.8.4. 

Figure 20 Sketch of the transition zone film—Plateau border in a Scheludko cell, h is the film thickness and 6 is the contact angle subtended between the extrapolated meniscus (the dashed line) and the film midplane.

The direct measurement of the disjoining pressure as a function of film thickness can be achieved by the thin film balance introduced by Derjaguin et al. [91] and Scheludko and Exerowa [768]. The principle of this so-called Scheludko cell is shown in Figure 7.6. The film is formed within a ring with 2—4 mm diameter. A small hole at the side of the ring allows to draw Uquid from the film and thus adjust and measure the capillary pressure applied. The film thickness is deduced via optical interferometry. Almost exclusively aqueous solutions are studied. Originally, the thin film balance was constructed to measure the force across foam films. Modified versions are also used to measure forces across emulsion films [732, 734]. 

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