Wetting characteristics of oil droplet in water on micro/nano pyramid array surfaces

The interaction mechanism between oil droplets and solid surfaces is explored, which is of great significance for the development of functionalized surfaces and the efficient coalescence of oil droplets in water. Based on the volume of fluid (VOF) model, numerical simulations are employed to analyze the wetting and spreading behavior of oil droplets on pyramid-textured surfaces. The influence of microstructure morphology and size on droplet spreading patterns, diffusion distance, and wetting behavior is systematically investigated. The results show that the spreading morphology of oil droplets is significantly influenced by microstructure geometry. Asymmetric pyramid structures (e.g., triangular and pentagonal pyramids) guide oil droplets to accelerate wetting along ridge directions, while symmetric pyramid structures (e.g., square and hexagonal pyramids) promote preferential filling of groove regions. The analysis of diffusion distances and pressure variations at the droplet center on different structured surfaces reveals that the pentagonal pyramid surface exhibits the largest spreading radius, whereas the triangular pyramid surface enhances droplet wettability on hydrophilic surfaces. Additionally, appropriately increasing the microstructure size reduces droplet adhesion, improves detachment efficiency, and optimizes the spreading morphology, thereby enhancing controllability over droplet movement direction.