Ref HAL: hal-01427072_v1
Ref Arxiv: 1604.02360
DOI: 10.1103/PhysRevFluids.1.083302
WoS: 000390345900001
Ref. & Cit.: NASA ADS
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8 Citations
Résumé:

We investigate the dynamics of freely expanding liquid sheets prepared with fluids with different rheological properties, (i) viscous fluids with a zero-shear viscosity $\eta_0$ in the range $(1-1000) \, \mathrm{mPa.s}$ and (ii) viscoelastic Maxwell fluids whose elastic modulus, $G_0$, characteristic relaxation time, $\tau$, and zero-shear viscosity, $\eta_0=G_0 \tau$, can be tuned over several orders of magnitude. The sheets are produced by impacting a drop of fluid on a small cylindrical solid target. For viscoelastic fluids, we show that, when $\tau$ is shorter than the typical lifetime of the sheet ($\sim 10$ ms), the dynamics of the sheet is similar to that of Newtonian viscous liquids with equal zero-shear viscosity. In that case, for little viscous samples ($\eta_0 <\sim 30$ mPa.s), the maximal expansion of the sheet, $d_{\rm{max}}$, is independent of $\eta_0$, whereas for more viscous samples, $d_{\rm{max}}$ decreases as $\eta_0$ increases. We provide a simple model to account for the dependence of the maximal expansion of the sheet with the viscosity that is based on an energy balance between inertia, surface tension and viscous shear dissipation on the solid target, and which accounts well for our experimental data. By contrast, when $\tau$ is longer than the typical lifetime of the sheet, the behavior drastically differs. The sheet expansion is strongly enhanced as compared to that of viscous samples with comparable zero-shear viscosity, but is heterogeneous with the occurrence of cracks, revealing the elastic nature of the viscoelastic fluid.

Ref HAL: hal-02070634_v1
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The Continuous Droplet Interface Crossing Encapsulation (cDICE) is an easy and robust method for producing, at high yield, monodisperse lipid vesicles with a controlled content as well as capsules with a designed shell. It consists in forcing a droplet through an interface between two imiscible fluids, using an external force such as centrifugation. At high inertia, the droplet entrain fluid that will constitute the shell of the capsule. At low inertia, the presence of amphiphile and the deformable interface interactions lead to monolayers zipping and formation of an amphiphile bilayer around the droplet. We will discuss the physical mechanisms involved in the production of both cDICE vesicles (low droplets inertia) and capsules (at high inertia), and the potential applications of this method. This method founds indeed many applications in biomimetics as it allows to encapsulate various biological solutions (biopolymers, hemoglobin, colloids, polymeric gels, cells. . . ) in membranes that can be composite and/or assymetric, or polymeric, and in the field of microencapsulation.

Ref HAL: hal-02070620_v1
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The Continuous Droplet Interface Crossing Encapsulation (cDICE) is an easy and robust method for producing, at high yield, monodisperse lipid vesicles with a controlled content as well as capsules with a designed shell. It consists in forcing a droplet through an interface between two imiscible fluids, using an external force such as centrifugation. At high inertia, the droplet entrain fluid that will constitute the shell of the capsule. At low inertia, the presence of amphiphile and the deformable interface interactions lead to monolayers zipping and formation of an amphiphile bilayer around the droplet. We will discuss the physical mechanisms involved in the production of both cDICE vesicles (low droplets inertia) and capsules (at high inertia), and the potential applications of this method. This method founds indeed many applications in biomimetics as it allows to encapsulate various biological solutions (biopolymers, hemoglobin, colloids, polymeric gels, cells. . . ) in membranes that can be composite and/or assymetric, or polymeric, and in the field of microencapsulation.

Ref HAL: hal-02066409_v1
DOI: 10.1039/C6FD90050J
WoS: 000385257300023
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1 Citation

Ref HAL: hal-02060816_v1
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Polyion Complex (PIC) or Complex Coacervate Core (C3M) Micelles [1] have been used as structuring agents to template ordered mesostuctured porous silica materials [2]. PIC micelles assemble by electrostatic complexation of oppositely charged polyelectrolytes, one of them being a double hydrophilic block copolymer (DHBC). Compared to classical structuring agents obtained from amphiphilic molecules, PIC micelles offer several advantages: first, they can be recovered and reused in several mesoporous material synthesis cycles [2]. Secondly, they allow single step preparation of drug loaded porous materials [3]. Finally, tuning the characteristics of the porous material does no longer require the synthesis of new structuring agents: they can be adjusted by playing with the physico-chemical conditions, using a unique polyelectrolyte system. The present work aims at correlating the characteristics of the porous materials and the physico-chemical properties of the PIC micelles.Mesostructured materials have been prepared by condensation of TEOS in the presence of PIC micelles of polyethylene oxide-b-poly(acrylic acid) (POE-b-PAA) copolymer complexed with neomycin (NM) or oligochitosan (OC). TEM, sorption measurements and X-ray diffraction have shown that varying structures and pore sizes can be achieved by simply varying concentration and pH. On the other hand, using osmometry, specific ion potentiometry, elemental analysis and small angle X-ray scattering, the associative phase separation of poly(acrylic acid) in the presence of neomycin has been studied as a model system for the core of the PIC micelles.The hybrid materials obtained right after drying (without calcination) are porous. This is related to the high degree of swelling of the core of the PIC micelles that contains at least 50% of water in weight. The water content in the micelles varies with concentration because it is determined by osmotic equilibrium between the core and the suspending solution. This translates into variation of porous volume and allows fine tuning of the pore size in the hybrid material. These features are preserved after calcination. Finally, the pH of material synthesis has been shown to determine the drug loading: neomycin concentration in the hybrid porous material increases as pH increases.In conclusion, PIC micelles offer numerous advantages and opportunities in the domain of functional ordered mesostructured materials due to the sensitivity of their characteristics to physico-chemical parameters, allowing the reversibility of their assembling in water, the possible delivery of functional molecules and the possibility to control the swelling of PIC micelles core.References: [1] Voets, I. K.; de Keizer, A.; Stuart, M. A. C. Adv. Colloid Interface Sci., 2009, 147-48, 300-318.[2] Baccile, N.; Reboul, J.; Blanc, B.; Coq, B.; Lacroix-Desmazes, P.; In, M.; Gerardin, C. Angew. Chem. Int. Ed., 2008. 47(44), 8433-8437.[3] Molina, E.; Warnant, J.; Mathonnat, M.; Bathfield, M.; In, M.; Laurencin, D.; Jérôme, C.; Lacroix Desmazes, P.; Marcotte, N.; Gérardin, C. Langmuir, 2015. 31, 12839-12844.

Ref HAL: hal-02019637_v1
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Mechanical behavior of wheat endosperm. Local measurements by AFM and numerical modeling

Ref HAL: hal-01959931_v1
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