Variation of Local Surface Properties of an Air Bubble in Water Caused by Its Interaction with Another Surface

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• 作者：Lorena A. Del Castillo ; Satomi Ohnishi ; Steven L. Carnie ; Roger G. Horn
• 刊名：Langmuir
• 出版年：2016
• 出版时间：August 2, 2016
• 年：2016
• 卷：32
• 期：30
• 页码：7671-7682
• 全文大小：517K
• 年卷期：0
• ISSN：1520-5827

文摘

Surface and hydrodynamic forces acting between an air bubble and a flat mica surface in surfactant-free water and in 1 mM KCl solution have been investigated by observing film drainage using a modified surface force apparatus (SFA). The bubble shapes observed with the SFA are compared to theoretical profiles computed from a model that considers hydrodynamic interactions, surface curvature, and disjoining pressure arising from electrical double layer and van der Waals interactions. It is shown that the bubble experiences double-layer forces, and a final equilibrium wetting film between the bubble and mica surfaces is formed by van der Waals repulsion. However, comparison with the theoretical model reveals that the double-layer forces are not simply a function of surface separation. Rather, they appear to be changed by one of more of the following: the bubble’s dynamic deformation, its proximity to another surface, and/or hydrodynamic flow in the aqueous film that separate them. The same comments apply to the hydrodynamic mobility or immobility of the air–water interface. Together the results show that the bubble’s surface is “soft” in two senses: in addition to its well-known deformability, its local properties are affected by weak external forces, in this case the electrical double-layer interactions with a nearby surface and hydrodynamic flow in the neighboring aqueous phase.