A Microtensiometer To Probe the Effect of Radius of Curvature on Surfactant Transport to a Spherical Interface

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• 作者：Nicolas J. Alvarez ; Lynn M. Walker ; Shelley L. Anna
• 刊名：Langmuir
• 出版年：2010
• 出版时间：August 17, 2010
• 年：2010
• 卷：26
• 期：16
• 页码：13310-13319
• 全文大小：1052K
• 年卷期：v.26,no.16(August 17, 2010)
• ISSN：1520-5827

文摘

Diffusion of surfactant to a spherical interface depends on the radius of curvature of the interface; the smaller the radius of curvature is, the faster the dynamics. This paper presents and validates an experimental apparatus, denoted a “microtensiometer”, to study the dependence of surfactant dynamics on radius of curvature. Dynamic surface tension is monitored for a range of bubble radii from 17 to 150 μm, and the dynamics are compared with those obtained using the classic pendant drop experiment for a nonionic surfactant at the air−water interface. Experiments reveal that dynamic surface tension follows a diffusion-limited scaling, in which radius of curvature is a key parameter. Despite the clear scaling behavior of the experimental equilibration time, the full dynamic curve for an initially clean interface cannot be predicted by a diffusion-limited transport model using the molecular diffusion coefficient and a single isotherm. However, the same model is shown to correctly predict compression−expansion experiments. Aside from elucidation of surfactant transport, this device provides a tool for rapid measurements of interfacial properties using a significantly lower volume of sample than current methods.