Effect of Permeability on Aqueous Biopolymer Interfaces in Spinning Drop Experiments

Scholten, Elke; Sagis, Leonard M.C.; Linden, Erik van der

doi:10.1021/bm060251l

Cited by 15 publications

(29 citation statements)

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“…However, it was recently reported that the centrifugal field that is applied in this method, significantly affects the compositions of coexisting liquid phases. Demixed systems can even be brought into the one-phase regime [4].The method that is presented in this Letter does not rely on optical contrast, density differences, or strong external fields. We use colloidal probe atomic force microscopy (CP-AFM), introduced independently by Ducker et al [5] and Butt [6], to measure equilibrium forces originating from capillary, liquid bridges between two surfaces.…”

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confidence: 99%

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Equilibrium Capillary Forces with Atomic Force Microscopy

et al. 2007

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We present measurements of equilibrium forces resulting from capillary condensation. The results give access to the ultralow interfacial tensions between the capillary bridge and the coexisting bulk phase. We demonstrate this with solutions of associative polymers and an aqueous mixture of gelatin and dextran, with interfacial tensions around 10 N=m. The equilibrium nature of the capillary forces is attributed to the combination of a low interfacial tension and a microscopic confinement geometry, based on nucleation and growth arguments. DOI: 10.1103/PhysRevLett.99.104504 PACS numbers: 47.55.nk, 68.03.Cd, 68.37.Ps Interfaces are ubiquitous in soft matter and biological systems. The corresponding phase equilibria are often characterized by weak, tunable interactions and large length scales . As a result, the interfacial tensions, / k B T= 2 , are typically ultralow (i.e., 1 mN m ÿ1 ). Measurement of ultralow interfacial tensions is notoriously difficult. Many available techniques, such as drop shape [1] or interfacial profile analysis [2], rely on optical visualization. However, in weakly segregated and nearcritical systems, the optical contrast between the phases is generally small. Moreover, density differences are also small, because of which it is difficult to obtain accurate information from drop shape analysis under normal gravity. To induce larger deformations, the spinning drop method is commonly used [3]. However, it was recently reported that the centrifugal field that is applied in this method, significantly affects the compositions of coexisting liquid phases. Demixed systems can even be brought into the one-phase regime [4].The method that is presented in this Letter does not rely on optical contrast, density differences, or strong external fields. We use colloidal probe atomic force microscopy (CP-AFM), introduced independently by Ducker et al. [5] and Butt [6], to measure equilibrium forces originating from capillary, liquid bridges between two surfaces. We analyze the resulting force-separation profiles to extract ultralow interfacial tensions. In Fig. 1 we show a schematic representation of a capillary, liquid bridge between a sphere and a flat substrate, the characteristic configuration in the CP-AFM experiment.When a homogeneous phase, in which one of the components is near its saturation point, is confined between two surfaces, a new phase can be formed by either condensation or evaporation. It is well known that, e.g., water condenses between hydrophilic surfaces in humid air [7]. Between hydrophobic surfaces at close separation, immersed in pure water, a capillary bridge of water vapor is formed, a process known as capillary evaporation or cavitation [8]. Capillary condensation is also reported for systems that show liquid-liquid coexistence, e.g., demixed ternary polymer-solvent systems [9]. Because the curvature of the capillary bridge is negative with respect to the inner phase, a negative pressure difference is present across the interface, leading to an attractive force between the ...

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Equilibrium Capillary Forces with Atomic Force Microscopy

et al. 2007

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“…That mass transfer can have an appreciable effect on the dynamic behavior of a deformed droplet was also shown in recent interfacial tension measurements of biopolymer solutions, using the spinning drop method [6]. Droplets deformed by spinning the capillary, slowly dissolved, and the rate of dissolution increased with increasing spinning rate, or increasing deformation of the droplets.…”

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“…In these systems water and dissolved molecules can transfer easily from one aqueous bulk phase to the other. This high permeability of the interface has a significant effect on the stressdeformation and deformation-relaxation behavior of, for example, droplets in phase-separated biopolymer solutions [4,5].That mass transfer can have an appreciable effect on the dynamic behavior of a deformed droplet was also shown in recent interfacial tension measurements of biopolymer solutions, using the spinning drop method [6]. Droplets deformed by spinning the capillary, slowly dissolved, and the rate of dissolution increased with increasing spinning rate, or increasing deformation of the droplets.…”

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Fluctuations of Permeable Interfaces in Water-in-Water Emulsions

Sagis

2007

Phys. Rev. Lett.

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The fluctuations of highly permeable interfaces, encountered in phase-separated biopolymer solutions, liposomes, polymersomes, or colloidosomes, are investigated. An expression for the power spectrum of the height correlation function is derived for a multicomponent system, incorporating the effects of mass transfer across the interface, using nonequilibrium thermodynamics. We also derive an expression for the relaxation time of the height correlation function, and calculate the relaxation time for a phase-separated gelatin-dextran-water system. Comparing our expression with the expression for an impermeable interface shows that mass transfer has a significant impact on the relaxation time of the interface. DOI: 10.1103/PhysRevLett.98.066105 PACS numbers: 68.35.Ja, 68.05.ÿn Water-in-water emulsions, such as phase-separated (bio)polymer solutions, liposomes, polymersomes, or colloidosomes, can be used for encapsulation and texturing applications in pharmaceutical, food, or cosmetic products. The interfaces in these emulsions have properties that differ significantly from those found in oil-water or water-air systems, stabilized by a simple surfactant. The interfacial tension in water-in-water emulsions is often extremely low. For example, in phase-separated biopolymer solutions the surface tension is of the order of 10 ÿ6 N=m [1]. The bending rigidity of interfaces in these systems can be significant, as high as 500 kT [2]. As a result, the bending rigidity can have an appreciable effect on the dynamic behavior of these systems [3].Another important property of the interfaces in water-inwater emulsions is their permeability. In these systems water and dissolved molecules can transfer easily from one aqueous bulk phase to the other. This high permeability of the interface has a significant effect on the stressdeformation and deformation-relaxation behavior of, for example, droplets in phase-separated biopolymer solutions [4,5].That mass transfer can have an appreciable effect on the dynamic behavior of a deformed droplet was also shown in recent interfacial tension measurements of biopolymer solutions, using the spinning drop method [6]. Droplets deformed by spinning the capillary, slowly dissolved, and the rate of dissolution increased with increasing spinning rate, or increasing deformation of the droplets.In previous work we used scaling analysis to study the effects of permeability and bending rigidity on the dynamic behavior of phase-separated biopolymer solutions [4 -6]. In systems with a composition close to the critical point, we observed that the relaxation time of the system scales as L 4 = p k , with L a characteristic length scale of the system, p the permeability of the interface, and k the bending rigidity. In systems with a composition far from the critical point, relaxation is dominated by surface tension and permeability, andHere we will use a more formal approach, using nonequilibrium thermodynamics to derive expressions for the power spectrum of the height correlation function and the relaxa...

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Engineered food microstructure for enhanced quality and stability

Scholten

2018

Food Microstructure and Its Relationship With Quality and Stability

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Effect of Permeability on Aqueous Biopolymer Interfaces in Spinning Drop Experiments

Cited by 15 publications

References 20 publications

Equilibrium Capillary Forces with Atomic Force Microscopy

Equilibrium Capillary Forces with Atomic Force Microscopy

Fluctuations of Permeable Interfaces in Water-in-Water Emulsions

Engineered food microstructure for enhanced quality and stability

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