Dresden 2017 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 12: Focus: Soft Particles in Flows II (joint focus session CPP/DY)
CPP 12.10: Talk
Monday, March 20, 2017, 17:45–18:00, ZEU 160
Dynamics of microcapsules in elongational and shear flows — •Clement de Loubens1, Kaili Xie2, and Marc Leonetti3 — 1Laboratoire Rheologie et Procedes, Grenoble, France — 2M2P2, Marseille, France — 3IRPHE, Marseille, France
A capsule is a drop bounded by a thin solid membrane providing specific mechanical properties. The interfacial rheological properties of these soft microparticles are deduced from their dynamics of deformation in elongational and shear flows.
In elongational flow, the surface shear modulus of the membrane is measured and related to the kind of biopolymer used and to the main parameters of the process of fabrication. In the regime of large deformations, the microcapsules can present a non-linear elastic response or plastic deformations. Non-linear elastic constitutive law is deduced by comparison of the evolution of the shape of the microcapsule in the two main planes of deformation of the capsule with numerical simulations.
In shear flow, the rotation of the membrane, i.e. the tank-treading, is visualised and quantified by decorating the membrane of microcapsules with particles. The tracking of the distance between two close microparticles showed membrane contraction at the tips and stretching on the sides. This dynamics of deformation induce viscous dissipation inside the membrane. The order of magnitude of membrane viscosity is determined by comparison with numerical simulations.
We will conclude the talk by some examples of breakdown of microcapsules in elongational flow.