Shirota Minori, van Limbeek Michiel A J, Lohse Detlef, Sun Chao
Faculty of Science and Technology, Hirosaki University, 0368561, Aomori, Japan.
Physics of Fluids Group, Mesa+ Institute, University of Twente, 7500, AE Enschede, The Netherlands.
Eur Phys J E Soft Matter. 2017 May;40(5):54. doi: 10.1140/epje/i2017-11542-4. Epub 2017 May 9.
In the study of interactions between liquids and solids, an accurate measurement of the film thickness between the two media is essential to study the dynamics. As interferometry is restricted by the wavelength of the light source used, recent studies of thinner films have prompted the use of frustrated total internal reflection (FTIR). In many studies the assumption of a simple exponential decay of the intensity with film thickness was used. In the present study we highlight that this model does not satisfy the Fresnel equations and thus gives an underestimation of the films. We show that the multiple reflections and transmissions at both the upper and the lower interfaces of the film must be taken into account to accurately describe the measured intensity. In order to quantitatively validate the FTIR technique, we measured the film thickness of the air gap between a convex lens of known geometry and a flat surface and obtain excellent agreement. Furthermore, we also found that we can accurately measure the elastic deformations of the lens under loads by comparing them with the results of the Herzian theory.
在液体与固体相互作用的研究中，精确测量两种介质之间的薄膜厚度对于研究动力学至关重要。由于干涉测量法受所用光源波长的限制，近期对更薄薄膜的研究促使人们使用受抑全内反射（FTIR）。在许多研究中，采用了强度随薄膜厚度呈简单指数衰减的假设。在本研究中，我们强调该模型不满足菲涅耳方程，因此会低估薄膜厚度。我们表明，为了准确描述测量强度，必须考虑薄膜上下界面处的多次反射和透射。为了定量验证FTIR技术，我们测量了已知几何形状的凸透镜与平面之间气隙的薄膜厚度，并获得了极佳的一致性。此外，我们还发现，通过将透镜在负载下的弹性变形与赫兹理论的结果进行比较，能够准确测量这些变形。
