Wetting kinetics of nanodroplets on lyophilic nanopillar-arrayed surfaces: A molecular dynamics study

Dynamic Spreading of Droplets on Lyophilic Micropillar-Arrayed Surfaces

“…The inset in Figure b shows the topological parameters for experimental substrates, where W , S , and H represent the width, spacing, and height of the pillar, respectively. The φ s is defined as φ s = W 2 / S 2 . In the experiments, the substrates were cleaned with methylbenzene, ultrapure water, and 99.5% ethanol with sequential ultrasonication and were dried using pure nitrogen.…”

“…Kim et al found that the effects of volume change on wetting are insignificant at the early stage. Because the effects of the change in volume are insignificant, the focus in the majority of related studies ,− , and in this study is the early spreading, which is valuable to reveal the unique wetting kinetics of lyophilic micropillar-arrayed surfaces. With a multiscale combination method of experiments and molecular dynamics simulations, Yuan and Zhao found that lyophilic pillars on square micropillar-arrayed Si surfaces not only provide excess driving force but also pin the liquid around the pillars.…”

“…Kim et al reported that the early spreading of bulk droplets and the propagation of fringe films can be analyzed separately due to the different dynamics of droplet spreading on the square micropillar-arrayed Si surfaces. Zong et al studied the early spreading of water droplets on lyophilic nanopillar-arrayed substrates using molecular dynamics simulations and found that the propagation of fringe film is hindered by the enhanced solid wettability. The hindered effect is mainly caused by the extra energy barrier introduced by the interactions between the nanopillars and water molecules, which increases with the solid wettability .…”

“…Zong et al studied the early spreading of water droplets on lyophilic nanopillar-arrayed substrates using molecular dynamics simulations and found that the propagation of fringe film is hindered by the enhanced solid wettability. The hindered effect is mainly caused by the extra energy barrier introduced by the interactions between the nanopillars and water molecules, which increases with the solid wettability . Using Si nanorod-arrayed surfaces, Fan and Zhao found that the early spreading is independent of nanorod height.…”

“…In previous studies, ,− R b = Ct n remained in use to describe R b for lyophilic pillar-arrayed surfaces. Although, in general, R b = Ct n can well describe the experimental results by adjusting the pre-exponential factor and the spreading index, the fitted spreading index ( n ) at early stage was nonuniform in previous studies and ranged from 0.108 to 1/3. ,− Considering the liquid penetration into the space among the pillars, the bulk droplets spread on a solid–liquid composited surface (SLS). , The flow field of droplets may also be affected by the surface structures, such as pillar arrangement, solid area fraction of substrate (φ s ), and pillar height ( H ), which may lead to the nonuniform spreading index. In addition, a predictive model for wetting kinetics on lyophilic pillar-arrayed surface is required for practical application and future design.…”