Gentle Film Trapping Technique with Application to Drop Entry Measurements

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• 作者：Asen Hadjiiski ; Slavka Tcholakova ; Ivan B. Ivanov ; Theodor D. Gurkov ; and Edward F. Leonard
• 刊名：Langmuir
• 出版年：2002
• 出版时间：January 8, 2002
• 年：2002
• 卷：18
• 期：1
• 页码：127 - 138
• 全文大小：214K
• 年卷期：v.18,no.1(January 8, 2002)
• ISSN：1520-5827

文摘

The film trapping technique, FTT, allows one to investigate the interactions between colloidal particlesand a fluid interface that presses them against a flat solid substrate. The method was already applied formeasuring the contact angles of micrometer sized latex spheres (Hadjiiski, A.; Dimova, R.; Denkov, N. D.;Ivanov, I. B.; Borwankar, R. Langmuir 1996, 12, 6665.), and the interaction of white blood cells withadsorption layers of antibodies (Patrick, S. M.; An, H.; Harris, M. B.; Ivanov, I. B.; Braunshtein, N. S.;Leonard, E. F. Ann. Biomed. Eng. 1997, 25, 1072. Ivanov, I. B.; Hadjiiski, A.; Denkov, N. D.; Gurkov, T.D.; Kralchevsky, P. A.; Koyasu, S. Biophys. J. 1998, 75, 545.). A new modification of the equipment is nowproposed (FTT-gentle), which significantly increases the accessible range of capillary pressures exertedto particles, starting from a virtually zero value. This is particularly important for studying the highlydeformable particles (e.g., biological cells) or the oil drops, which easily coalesce with the interface, likethose used to promote a foam collapse (so-called antifoams). The basic principles of operation with FTT-gentle, illustrated with experiments and theoretical calculations of the shape of the interface around thetrapped particle and the position of the three-phase contact line at the particle surface, are described. Thefeasibility of FTT-gentle is demonstrated by measuring the drop entry barriers (the critical capillarypressure inducing the coalescence of drops with the air-water interface) of several antifoams. The resultsshow that the drop entry barrier strongly depends on the used surfactant and its concentration, and canbe significantly decreased by addition of hydrophobized solid particles in the oil drops.