Formation de capsules d’hydrogel à cœur aqueux par fragmentation d’un jet composé de fluides complexes

Abstract : The purpose of this work is to understand physical mechanisms that control the formation of aqueous-core submillimetric capsules with a thin hydrogel membrane. This comprehension will allow a better control of the process. Compound drops are first formed in the air by the break-up of a cylindrical jet composed of an aqueous core surrounded by an alginate solution. The shell is then solidified after immersion in a gelling calcium solution. The study of the co-flow inside the injector showed the existence of an elastic instability which is amplified in the presence of cations, due to the polyelectrolyte property of alginate.We showed that this instability causes the flapping of the compound jet out of the injector. The instability induces a displacement of the core fluid position which leads to an asymmetric velocity relaxation that creates a torque and finally bends the jet. We produced curved jets with a beveled capillary to demonstrate this effect. The jet break-up is controlled by a harmonic perturbation of the injection flow rates. We measured a decrease of the wave speed on the jet surface which is controlled by the surface tension. The alginate solution high viscosity causes an amplification of speed fluctuations that induces coalescence inside the jet. This amplification is enhanced by the addition of surfactants which create a dynamic surface tension at the jet interface. Finally, we managed to produce submillimetric and monodisperse capsules with a thin membrane, an encapsulation yield above 99% and a size that we can tune. These capsules can be used in biotechnology applications as a new tool for cell culture.
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https://pastel.archives-ouvertes.fr/tel-01095417
Contributor : Hugo Doméjean <>
Submitted on : Monday, December 15, 2014 - 3:44:28 PM
Last modification on : Thursday, July 4, 2019 - 11:00:05 AM
Long-term archiving on : Monday, March 16, 2015 - 12:06:25 PM

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Hugo Doméjean. Formation de capsules d’hydrogel à cœur aqueux par fragmentation d’un jet composé de fluides complexes. Physique [physics]. Université Pierre et Marie Curie, 2014. Français. ⟨tel-01095417⟩

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