Droplet splashing and retraction dynamics on micro/nano-textured surfaces with or without infused lubricants: an experimental approach

Critical Weber numbers ( We cr ) for droplet splashing are investigated by considering the geometrical morphologies of hydrophobic micro/nano-textured surfaces and the viscosity of lubricants. A decreasing trend of We cr with respect to pillar spacing is evident for all textured and lubricant-infused surfaces (LISs), but it is independent of the pillar diameter effect. Additionally, the overall We cr of the LIS exceeded that of the micro/nano-textured surfaces. The results show that the early droplet splash on micro/nano-textures may be attributed to the slip condition, decreasing the friction loss of airflow and increasing U air / U 0 and K-H instability. Moreover, the slip velocity on the LISs decreases as the lubricant viscosity increases in the order u slip (101) > u slip (105) > u slip (107). Therefore, an increase in slip velocity facilitates earlier droplet splashing on low-viscosity LIS101 than on high-viscosity LIS105 and LIS107. Furthermore, the droplet retraction behavior beyond the maximum spreading varied significantly based on the surface wetting characteristics.