Spreading of a droplet accompanying with an interaction with a spherical particle settled on a smooth substrate

Objective of this study is to elucidate experimentally the phenomenon that the macroscopic contact line (M-CL) of a droplet spreading on a horizontal substrate accelerates due to interaction with a spherical particle. We observed the temporal variation of the M-CL rising on the spherical particle and the liquid film profile near the contact line around the particle under low capillary number condition. It was found that the particle still remains settled on the substrate even after the interaction with the front edge of the droplet under smaller capillary number in the present condition. The particle is sucked toward the bulk of the droplet by the interaction with the droplet under moderate capillary number condition. We will discuss the condition of the M-CL acceleration from the shape of the meniscus.