Fabrication, characterization and modeling of CAPSules under HYDRodynamic stresses – CAPSHYDR

Encapsulation consists in protecting a substance with a solid envelope. It avoids its dispersion in the ambient environment or its degradation in contact with it. The use of capsules (encapsulated liquid droplets) is common in nature (red blood cells, phospholipid vesicles) and in different industrial applications (biotechnology, pharmacology, cosmetics, food industry). The particles studied in this project are micrometric in size (from a few tens to a few hundreds of microns), have a liquid internal medium and are to be used in suspension in another liquid. Their membrane is a lipid bilayer (vesicles) or a reticulated membrane with elastic properties (capsules). The use of these particles relies on a fine control of the membrane properties, to control their deformation or possible breakup (to be induced or prevented depending on the application). Controlling the membrane properties is essential to optimize the design and production of specific capsules for each application.
The objectives of the multidisciplinary project are the following:
• Influence of the fabrication process on the physical and mechanical properties of the capsule (shape, size, degree of reticulation, membrane mechanical properties).
• Motion and deformation of capsules and vesicles in suspension in an external fluid environment in motion: different experimental setups will be designed and built in order to study the large deformations of these particles. The flows that will be studied are the flow in micrometric pores of variable cross-section, simple shear flows and elongational flows. One of the objectives is to generate high enough hydrodynamic forces to lead to the deterioration of the particles (breakup, filament formation).
• Numerical modeling of the motion and deformation of capsules and vesicles in suspension in a fluid flow. We will have to model the interactions between the internal and external flows and the large deformations of the membrane. The numerical study will help us predict the deformation of capsule/vesicle depending on their intrinsic physical properties, evaluate the membrane mechanical properties from experimental observations, provide the values of non-measurable quantities such as the stress level in the membrane in order to evaluate the risk of rupture.
• The coupled study of capsules and vesicles will enable us to clearly identify the similarities and differences between the two types of particles.
• The final objective of the project is to set up devices for the mechanical characterization of capsules and vesicles.

The project covers various fields of research that include continuum mechanics, physics, chemistry, polymer reticulation and pharmaceutical technology. The interdisciplinary consortium is composed of teams with complementary fields of expertise. Each team is recognized as leader in its field of research. BMBI will bring its expertise in the theoretical, numerical and experimental modeling of capsules in flow. IRPHE has a strong experience in the study of vesicles as well as an expertise in microfluidic experimental techniques. M2P2 will bring its expertise in the numerical modeling of vesicles. ICMR, specialized in molecular chemistry, will bring its expertise in the fabrication and characterization of capsules.