Abstract
Wetting and dewetting of the solid material by the liquid are focused. They can be observed in many natural phenomena and technological applications; such as falling rain droplet on the window, boiling, thin film coating, and crystal growth. These processes are accompanied with the movement of the boundary line of three phases; solid-liquid-gas interface, which is so-called macroscopic 'contact line'. The authors focus on the dynamics of the droplet traveling on the solid substrate accompanying with 'precursor film' ahead the contact line of the droplet. The precursor film was detected by applying conventional ellipsometer, and its existing length was evaluated as a function of a dimensionless Capillary number. The authors also indicate the effect of gravity upon the existing length of precursor film.
