Interactions of Oil Drops Induced by the Lateral Capillary Force and Surface Tension Gradients

The interacting forces on the objects at the air-liquid interface are important for researching self-assembly of objects. Due to the interacting forces among objects, the objects self-assemble at the air-liquid interface and organize into ordered structures. In general, for the interacting of oil drops, they can attract coalescence or repel dispersion. However, according to our former research, we find that interactions of oil drops can be motion like interactions of gas atoms. The oil drops cannot coalesce to form a big oil drop or separate to form ordered structures. They attract at a long distance but repel when they almost contact. In this study, according to our simulation, we demonstrate that the atomic-like motion of oil drops is mainly caused by the surface tension gradient and the lateral capillary force. Based on the results, our research will facilitate the fundamental understanding about interactions among oil drops. Apart from giving detailed demonstration about the interacting forces among oil drops, our research may also put forward research about self-assembly, oil emulsification, and microfluidics.