ROLE OF INTERFACIAL PROPERTIES ON THE MOTION AND DEFORMATION OF CAPSULES IN SHEAR-FLOW

The influence of interfacial properties on the dynamics of a capsule freely suspended in a viscous liquid subjected to flow is assessed. First, the case of a liquid-liquid interface is considered: experimental evidence and theoretical models show that the drop deformation depends on the type of flow, the internal to external viscosity ratio and the capillary number, which measures the ratio between surface tension and viscous forces. Burst of the drop is predicted to occur when the normal stress equilibrium cannot be satisfied everywhere on the interface. Next, we consider the case of capsules, which are liquid drops enclosed by a solid deformable interface. From experiment and theoretical models, they are known to deform and to burst in some cases. Their motion depends on essentially the same parameters as for liquid drops, but different interfacial constitutive laws lead to different types of deformation and motion.