Acceleration characteristics of macroscopic contact line induced by interactions of liquid film with micro spheres

Abstract

It has been reported that a rapid acceleration of a macroscopic contact line (MCL) during droplet spreading is induced by particles deposited on a hydrophilic surface. In this study, we quantitatively correlated the MCL acceleration with the size of a single sphere during the rapid motion of a liquid film on a silicon wafer or glass surface. The sphere coated with gold was used in our experiments. Power law relationships were identified between the maximum velocity and the acceleration period, as well as between the acceleration period and the initial velocity at which the MCL contacted the sphere. In addition, the acceleration period increases linearly with sphere diameter. In the acceleration period, the spreading distance of the liquid film from the liquid front to the particle centre was proportional to the diameter of the sphere. This study provides detailed information of dynamics of MCL acceleration during liquid spreading in the presence of micro particle interactions on a smooth hydrophilic surface. The findings will be helpful for improving wetting performances in the micro device.