Savulescu G C, Rücker M, Scanziani A, Pini R, Georgiadis A, Luckham P F
Norwegian University of Science and Technology, 7491 Trondheim, Norway.
Chemical Engineering, Imperial College London, SW7 2AZ, UK; Mechanical Engineering, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands.
J Colloid Interface Sci. 2021 Jun 15;592:397-404. doi: 10.1016/j.jcis.2021.02.070. Epub 2021 Feb 22.
Roughness is an important parameter in applications where wetting needs to be characterized. Micro-computed tomography is commonly used to characterize wetting in porous media but the main limitation of this approach is the incapacity to identify nanoscale roughness. Atomic force microscopy, AFM, however, has been used to characterize the topography of surfaces down to the molecular scale. Here we investigate the potential of using AFM to characterize wetting behavior at the nanoscale.
Droplets of water on cleaved calcite under decane were imaged using quantitative imaging QI atomic force microscopy where a force-distance curve is obtained at every pixel.
When the AFM tip passed through the water droplet surface, an attraction was observed due to capillary effects, such that the thickness of the water film was estimated and hence the profile of the droplet obtained. This enables parameters such as the contact angle and contact angle distribution to be obtained at a nanometer scale. The contact angles around the 3-phase contact line are found to be quasi-symmetrically distributed between 10-30°. A correlation between the height profile of the surface and contact angle distribution demonstrates a quasi-proportional relationship between roughness on the calcite surface and contact angle.
粗糙度是需要表征润湿性的应用中的一个重要参数。微型计算机断层扫描通常用于表征多孔介质中的润湿性，但这种方法的主要局限性在于无法识别纳米级粗糙度。然而，原子力显微镜（AFM）已被用于表征直至分子尺度的表面形貌。在此，我们研究使用AFM在纳米尺度表征润湿性的潜力。
使用定量成像（QI）原子力显微镜对癸烷下解理方解石上的水滴进行成像，其中在每个像素处获得力-距离曲线。
当AFM探针穿过水滴表面时，由于毛细作用观察到一种吸引力，从而估计出水膜的厚度，进而获得水滴的轮廓。这使得能够在纳米尺度获得诸如接触角和接触角分布等参数。发现三相接触线周围的接触角在10°至30°之间近似对称分布。表面高度轮廓与接触角分布之间的相关性表明方解石表面粗糙度与接触角之间存在近似比例关系。
