Hokkanen Matti J, Backholm Matilda, Vuckovac Maja, Zhou Quan, Ras Robin H A
Department of Applied Physics, Aalto University School of Science, Puumiehenkuja 2, 02150 Espoo, P.O. Box 15100, Aalto, FI-00076, Finland.
Department of Electrical Engineering and Automation, Aalto University School of Electrical Engineering, P.O. Box 15500, Aalto, FI-00076, Finland.
Adv Mater. 2021 Oct;33(42):e2105130. doi: 10.1002/adma.202105130. Epub 2021 Sep 1.
Superhydrophobic coatings have extraordinary properties like self-cleaning and staying dry, and have recently appeared on industrial and consumer markets. The stochastic nature of the coating components and coating processes (e.g., spraying, painting) affects the uniformity of the water repellency across the coated substrate. The wetting properties of those coatings are typically quantified on macroscale using contact angle goniometry (CAG). Here, highly sensitive force-based methods, scanning droplet adhesion microscopy (SDAM), and micropipette force sensor (MFS), are used, to quantify the microscale heterogeneity in the wetting properties of stochastic superhydrophobic coatings with irregular surface topography that cannot be investigated by CAG. By mapping the wetting adhesion forces with SDAM and friction forces with MFS, it is demonstrated that even the best coatings on the market are prone to heterogeneities that induce stick-slip motion of droplets. Thus, owing to their high spatial and force resolution, the advantages of these techniques over CAG are demonstrated.
超疏水涂层具有自清洁和保持干燥等非凡特性，最近已出现在工业和消费市场上。涂层成分和涂层工艺（如喷涂、涂装）的随机性会影响涂层基材上疏水性能的均匀性。这些涂层的润湿性通常在宏观尺度上使用接触角测量法（CAG）进行量化。在此，使用高灵敏度的基于力的方法、扫描液滴粘附显微镜（SDAM）和微量移液器力传感器（MFS），来量化具有不规则表面形貌的随机超疏水涂层润湿性的微观尺度不均匀性，而CAG无法对其进行研究。通过用SDAM绘制润湿性粘附力以及用MFS绘制摩擦力，结果表明，即使是市场上最好的涂层也容易出现导致液滴产生粘滑运动的不均匀性。因此，由于其高空间分辨率和力分辨率，这些技术相对于CAG的优势得以彰显。
