Quantitative measurements of the lift force acting on a sphere sliding along a liquid–liquid interface

This work explores the lift force experienced by a particle moving in a viscous fluid near a liquid-liquid interface. The lift force is induced by the interaction between the viscous flow generated by the particle's motion and the deformation of the soft interface. The factors influencing the lift force including the velocity, the viscosity, and the sphere radius, and the separation distance were systematically studied. The experiments demonstrate that the lift force intensifies as the particle approaches the interface, and saturates at shorter distances. These findings are consistent with predictions made using soft lubrication theory and numerical calculations, providing strong validation for the theoretical framework.