Effect of Shear Flow on the Phase Behavior of an Aqueous Gelatin−Dextran Emulsion

Antonov, Yu. A.; Puyvelde, Peter Van; Moldenaers, Paula; Leuven, KU

doi:10.1021/bm0300352

“…www.chemphyschem.org flow-induced structural anisotropy due to deformation of the emulsion droplets, [10,12,13] 2) anisotropy is much more pronounced for the surfactant-stabilized system as compared to the lysozyme system, 3) if the data in Figure 3 are plotted against the shear stress scaled by R/s, that is, against the capillary number, we find that the flow-induced morphology is qualitatively different for the protein. d = f(Ca) has a much lower slope, whereas we would expect that if the only interfacial effect of the lysozyme were a decrease in interfacial tension, its d vs Ca results should coincide with the ones measured with SDS as the surfactant.…”

mentioning

confidence: 92%

“…[13] In both cases, the delicate balance of interfacial to hydrodynamic stresses is in a range in which drop sizes, time scales and shear stresses are experimentally accessible to mechanical and optical measurements. The hydrodynamic and surface chemical parameters of the system can be combined into a dimensionless quantity, the capillary number Ca = tR=s, which is the ratio of hydrodynamic (t) to interfacial stresses (s/R), where s is the static interfacial tension and R the radius of the undeformed drop.…”

mentioning

confidence: 99%

“…[10] Flow-induced shape anisotropy of emulsion drops in the mm size range can be studied by rheo small-angle light scattering (Rheo-SALS). [2,12,10,13] Such measurements have been achieved for blends of immiscible polymers, where absolute viscosities are very high, [12] and in phasesegregated biopolymer mixtures, where interfacial tensions between two different aqueous phases are very low. [13] In both cases, the delicate balance of interfacial to hydrodynamic stresses is in a range in which drop sizes, time scales and shear stresses are experimentally accessible to mechanical and optical measurements.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Complex Interfaces and their Role in Protein‐Stabilized Soft Materials

Erni

¹

,

Fischer

²

,

Herle

³

et al. 2008

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Proteins adsorbed at fluid interfaces are pivotal for the stability and flow behavior of foams and emulsions, [1][2][3] the mechanics of cell membranes, [4] and interfacial enyzme catalysis.[5] Besides a reduction in the interfacial tension, protein aggregation at the phase boundary leads to distinctive local mechanics of the interface. [1,[6][7][8] The contribution of such interfacial viscoelasticity to the macroscopic stability and flow behavior of high internal interface materials is still poorly understood. We study the interfacial mechanics of adsorption layers formed by the globular protein lysozyme and relate them to the morphology of emulsions stabilized by the same protein. A scaling analysis accounting for structural anisotropy, interfacial tension and the drop size reveals that emulsion drops stabilized by an adsorption layer of globular proteins can be seen as capsules surrounded by a soft shell. Besides its relevance for the rheology and stability of emulsions and foams, this insight is of fundamental importance for the design and controlled self-assembly of protein-based delivery systems, such as nanocapsules or colloidosomes. [9] Emulsions, immiscible polymer blends, and phase-separated biopolymer mixtures develop flow-induced morphologies if the stresses due to the applied flow field can overcome the capillary forces that favor a spherical drop morphology at rest. [10][11][12] Drops are subjected to deformation, break-up, and coalescence, all of which are associated with characteristic light scattering patterns.[10] Flow-induced shape anisotropy of emulsion drops in the mm size range can be studied by rheo small-angle light scattering (Rheo-SALS).[2, 12, 10, 13] Such measurements have been achieved for blends of immiscible polymers, where absolute viscosities are very high, [12] and in phasesegregated biopolymer mixtures, where interfacial tensions between two different aqueous phases are very low. [13] In both cases, the delicate balance of interfacial to hydrodynamic stresses is in a range in which drop sizes, time scales and shear stresses are experimentally accessible to mechanical and optical measurements. The hydrodynamic and surface chemical parameters of the system can be combined into a dimensionless quantity, the capillary number Ca = tR=s, which is the ratio of hydrodynamic (t) to interfacial stresses (s/R), where s is the static interfacial tension and R the radius of the undeformed drop. Studies on emulsion stability and flow often focus on the interfacial tension (either static, transient, or dynamic) as the sole physical property of the phase boundary.[2] It is, however, well-known that surface-active molecules impart a variety of dynamic properties upon the interface. [1,3] Therefore, the interfacial tension, which in its common use is merely a two-dimensional analog of the hydrostatic pressure in a liquid, must be generalized to include compressional and shear stresses-it becomes a tensorial quantity that is a function of both the extent and the rate of deformation of the interfac...

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“…9 The use of ATPS can significantly alleviate the concerns on the detrimental effects of organic solvents to the bioactivity of proteins and the viability of cells. 10 With traditional methods for fabricating all-aqueous emulsions, such as vortex mixing 11 and homogenization, 12 the sizes and structures of the resultant all-aqueous emulsions can hardly be controlled. With recent progress in microfluidic technology, immiscible aqueous phases are precisely manipulated in microchannels, allowing the fabrication of all-aqueous emulsions and jets with excellent control.…”

Section: Introductionmentioning

confidence: 99%

All-aqueous multiphase microfluidics

Song¹,

Sauret²,

Shum³

2013

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Immiscible aqueous phases, formed by dissolving incompatible solutes in water, have been used in green chemical synthesis, molecular extraction and mimicking of cellular cytoplasm. Recently, a microfluidic approach has been introduced to generate all-aqueous emulsions and jets based on these immiscible aqueous phases; due to their biocompatibility, these all-aqueous structures have shown great promises as templates for fabricating biomaterials. The physico-chemical nature of interfaces between two immiscible aqueous phases leads to unique interfacial properties, such as an ultra-low interfacial tension. Strategies to manipulate components and direct their assembly at these interfaces needs to be explored. In this paper, we review progress on the topic over the past few years, with a focus on the fabrication and stabilization of all-aqueous structures in a multiphase microfluidic platform. We also discuss future efforts needed from the perspectives of fluidic physics, materials engineering, and biology for fulfilling potential applications ranging from materials fabrication to biomedical engineering.

show abstract

“…9 The use of ATPS can significantly alleviate the concerns on the detrimental effects of organic solvents to the bioactivity of proteins and the viability of cells. 10 With traditional methods for fabricating all-aqueous emulsions, such as vortex mixing 11 and homogenization, 12 the sizes and structures of the resultant all-aqueous emulsions can hardly be controlled. With recent progress in microfluidic technology, immiscible aqueous phases are precisely manipulated in microchannels, allowing the fabrication of all-aqueous emulsions and jets with excellent control.…”

Section: Introductionmentioning

confidence: 99%

All-aqueous multiphase microfluidics : from formation of liquid structures to synthesis of biomaterials

Song¹,

宋阳²

0

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Immiscible aqueous phases, formed by dissolving incompatible solutes in water, have been used in green chemical synthesis, molecular extraction and mimicking of cellular cytoplasm. Recently, a microfluidic approach has been introduced to generate all-aqueous emulsions and jets based on these immiscible aqueous phases; due to their biocompatibility, these all-aqueous structures have shown great promises as templates for fabricating biomaterials. The physico-chemical nature of interfaces between two immiscible aqueous phases leads to unique interfacial properties, such as an ultra-low interfacial tension. Strategies to manipulate components and direct their assembly at these interfaces needs to be explored. In this paper, we review progress on the topic over the past few years, with a focus on the fabrication and stabilization of all-aqueous structures in a multiphase microfluidic platform. We also discuss future efforts needed from the perspectives of fluidic physics, materials engineering, and biology for fulfilling potential applications ranging from materials fabrication to biomedical engineering. V C 2013 AIP Publishing LLC. [http://dx

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Effect of Shear Flow on the Phase Behavior of an Aqueous Gelatin−Dextran Emulsion

Cited by 30 publications

References 43 publications

Complex Interfaces and their Role in Protein‐Stabilized Soft Materials

Complex Interfaces and their Role in Protein‐Stabilized Soft Materials

All-aqueous multiphase microfluidics

All-aqueous multiphase microfluidics : from formation of liquid structures to synthesis of biomaterials

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