Stick-slip behavior of sessile drop on the surfaces with irregular roughnesses

• Published in: Chemical engineering research & design 2020-08, Vol.160, p.216-223
• Main Authors: Azadi Tabar, Mohammad, Shayesteh, Mohammad, Shafiei, Yousef, Ghazanfari, Mohammad Hossein
• Format: Article
• Language: English
• Subjects: Atomic force microscopy; Calcite; Contact angle; Diffraction; Dynamic contact angle; Fourier transforms; Gravitational effects; Irregular roughness; Laplace equation; Laplace transforms; Modeling; Physical properties; Polishing; Roughness; Slip; Spherical caps; Stick-slip motion; Surface roughness; Wetting
• ISSN: 0263-8762; 1744-3563
• DOI: 10.1016/j.cherd.2020.06.001

•The stick-slip behavior of drop on a surface with irregular roughness was analyzed.•The advancing contact angels did not oscillate with a constant amplitude.•An accurate model was developed to predict stick time based on the Laplace equation. In this work, sessile drop and low-bond axisymmetric drop shape analysis methods were coupled to provide some new aspects on stick-slip behavior as well as stick time of a drop on calcite surfaces. Slightly hydrophobic calcite surfaces typified with three irregular roughnesses were used to create irregular surfaces to mimic defects for the water-calcite-air systems. Polishing papers of 200, 600, and 1200 grit and a polishing machine were used to prepare surfaces. X-ray diffraction, energy dispersive X-ray spectroscopy, Fourier transform infrared, and atomic force microscopy techniques were employed to evaluate the chemical and physical properties of surfaces. A model was developed to predict stick time based on the Laplace equation to take into account the effect of gravity which is neglected in the spherical cap model. An irregular stick–slip behavior of the three-phase contact line was observed for different roughness levels. Increasing roughness level from nono-metric to micrometric scale induced variation of 77.4°, 9.0e−03mN/m, 1.23mN/m to 67°, 293.0e−03mN/m, 7.20mN/m for the datum contact angle, scaled energy barrier, and the unbalanced Young force per unit length, respectively. Comparison of the models predictions and the obtained experimental data of stick times in this work, showed that the developed model is more accurate than the spherical cap model. This work could provide new insights into the wetting phenomenon of surfaces with irregular roughnesses.