Acceleration of the Macroscopic Contact Line of a Droplet Spreading on a Substrate after Interaction with a Particle

Abstract

We focus on dynamic behavior of the macroscopic contact line (MCL) of a droplet spreading on a substrate after an interaction with a spherical particle settled on the substrate. We will show that there exist three different regimes of the MCL behavior for different ranges of the capillary number. In the case of a small capillary number, the MCL exhibits a sharp acceleration after the interaction with the particle that remains at its original position In the case of a large capillary number, on the other hand, the MCL advances without any significant variation of behavior produced by the interaction with the particle. The particle is sucked toward the bulk of the droplet after the interaction. In the case of a moderate capillary number, the MCL exhibits gradual acceleration after the interaction with the particle, accompanied by a slight movement of the particle toward the droplet. We will also discuss the effect of the particle size on the behaviors of the MCL.