Morphology of Liquid Drops and thin Films on a Solid Surface with Sinusoidal Microstructures

Surface microstructures of solid materials play a significant role in various wetting and dewetting phenomena. In the present paper, the effect of micro- and nano-structures of a substrate surface on the morphology and evolution of liquid droplets and thin films is examined. The governing equations satisfied by droplets and films on a sinusoidal surface are derived by considering van der Waals force, surface tension, gravity and hydrostatic pressure. The morphologies of both liquid droplets and thin films are numerically simulated under various characteristic sizes of roughness. It is found that the droplet shapes show a significant dependence upon the characteristic sizes of substrate microstructures. A thin liquid film on a hydrophilic substrate may have a horizontal surface or replicate the substrate morphology, depending on the wavelength of roughness.The project supported by the National Natural Science Foundation of China (10525210, 10121202) and the Ministry of Education of China.The English text was polished by Keren Wang.