Recently,there are hesitations in the application scope of the classical Cassie theory and Wenzel theory.In this paper,Molecular Dynamics(MD)simulations are used to study these two theories used in the nanoscale and f...Recently,there are hesitations in the application scope of the classical Cassie theory and Wenzel theory.In this paper,Molecular Dynamics(MD)simulations are used to study these two theories used in the nanoscale and find their limitations.The effect of parameters including solid fractions(or roughness factors),arrangement of pillars(with same solid fractions),pillar height,and droplet size on contact angles was investigated.It shows that the Cassie equation is suitable for droplets on uniform pillared surfaces including different solid fractions,arrangement of pillars and pillar height,when there is no meniscus of droplets.The Wenzel equation is also suitable for droplets on uniform pillared surfaces including different roughness factors,arrangement of pillars and pillar heights.Moreover,whether the droplet size has an influence on the contact angle depends on the pinned place of the contact line.In the Wenzel state,the contact line is pinned although increasing the droplet size,resulting in increasing the contact angle,while the contact angle decreases to the initial value again when the droplet size increases enough to allow the contact line moving to the next pillar.The results provide insights toward the wettability of droplets on surfaces in nanoscale.展开更多
基金This work was supported by the National Natural Science Foundation of China(51905315)Shandong Provincial Natural Science Foundation(ZR2019BEMO12)+3 种基金the Scientific Research Foundation of Shandong University of Science and Technology for Recruited Talents(2019RCJJ001)the Fundamental Research Funds for theCentral Universities(20CX02317A)the Opening Fund of National Engineering Laboratory of Offshore Gcophysical and Exploration Equipmentthe Project of Shandong Province Higher Educational Young Innovative Talent Introduction and Cultivation Team(Environment function material innovation team).
文摘Recently,there are hesitations in the application scope of the classical Cassie theory and Wenzel theory.In this paper,Molecular Dynamics(MD)simulations are used to study these two theories used in the nanoscale and find their limitations.The effect of parameters including solid fractions(or roughness factors),arrangement of pillars(with same solid fractions),pillar height,and droplet size on contact angles was investigated.It shows that the Cassie equation is suitable for droplets on uniform pillared surfaces including different solid fractions,arrangement of pillars and pillar height,when there is no meniscus of droplets.The Wenzel equation is also suitable for droplets on uniform pillared surfaces including different roughness factors,arrangement of pillars and pillar heights.Moreover,whether the droplet size has an influence on the contact angle depends on the pinned place of the contact line.In the Wenzel state,the contact line is pinned although increasing the droplet size,resulting in increasing the contact angle,while the contact angle decreases to the initial value again when the droplet size increases enough to allow the contact line moving to the next pillar.The results provide insights toward the wettability of droplets on surfaces in nanoscale.
