Liquid slip on a nanostructured surface.

We explored a liquid slip, referred to as the Navier slip, at liquid-solid interface. Such a slip is provoked by the physicochemical features of the liquid-solid system. The goal of this study was to investigate the effect of a nanoengineered surface structure on liquid slip by fabricating the self-assembly structure of nano Zinc oxide (n-ZnO). We have also examined how the liquid-solid surface interaction controlled by hydrophobic chemical treatment affects the liquid slip. The findings showed that liquid slip increases with decreasing the characteristic length scales (e.g., channel height and depth), resulting in drag reduction. It was also found that dewetted (Cassie) state due to the generation of air gap developed by n-ZnO was more critical for the liquid slip than the minimization of interface interaction. The linear and nonlinear Navier slip models showed that liquid slip behavior is more obvious when increasing the nonlinearity. This study will contribute to understanding of the underlying physics behind fluid slip phenomena, such as the Navier slip for Newtonian liquids and Maxwell's slip for Newtonian gases.