Capsule motion in flow: Deformation and membrane buckling

The objective of this review is to present the salient features of capsule mechanical behaviour under the influence of viscous deforming forces due to a flowing fluid. We focus on artificial capsules that are initially spherical with an internal liquid core and that are enclosed by a very thin hyperelastic membrane. Different constitutive laws, commonly used to describe the rheological behaviour of thin membranes, are presented. The motion and deformation of a single capsule freely suspended in a simple shear flow is presented as a function of membrane constitutive law and of initial pre-stress. The limitations of classical membrane models that neglect bending effects are discussed.