Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Normal stresses in surface shear experiments
    Sagis, L.M.C. - \ 2013
    The European Physical Journal. Special Topics 222 (2013)1. - ISSN 1951-6355 - p. 99 - 103.
    in-water emulsions - interfacial permeability - general formalism - bending rigidity - complex fluids - dynamics - viscoelasticity - thermodynamics - liquid/liquid - gas/liquid
    When viscoelastic bulk phases are sheared, the deformation of the sample induces not only shear stresses, but also normal stresses. This is a well known and well understood effect, that leads to phenomena such as rod climbing, when such phases are stirred with an overhead stirrer, or to die swell in extrusion. Viscoelastic interfaces share many commonalities with viscoelastic bulk phases, with respect to their response to deformations. There is however little experimental evidence that shear deformations of interfaces can induce in-plane normal stresses (not to be confused with stresses normal to the interface). Theoretical models for the stress-deformation behavior of complex fluid-fluid interfaces subjected to shear, predict the existence of in-plane normal stresses. In this paper we suggest methods to confirm the existence of such stresses experimentally.
    Protein transfer to membranes upon shape deformation
    Sagis, L.M.C. ; Bijl, E. ; Antono, L. ; Ruijter, N.C.A. de; Valenberg, H.J.F. van - \ 2013
    The European Physical Journal. Special Topics 222 (2013)1. - ISSN 1951-6355 - p. 61 - 71.
    blood-cell deformability - in-water emulsions - fat globule size - interfacial permeability - flow - drops - milk - dissolution - infections - adsorption
    Red blood cells, milk fat droplets, or liposomes all have interfaces consisting of lipid membranes. These particles show significant shape deformations as a result of flow. Here we show that these shape deformations can induce adsorption of proteins to the membrane. Red blood cell deformability is an important factor in several diseases involving obstructions of the microcirculatory system, and deformation induced protein adsorption will alter the rigidity of their membranes. Deformation induced protein transfer will also affect adsorption of cells onto implant surfaces, and the performance of liposome based controlled release systems. Quantitative models describing this phenomenon in biomaterials do not exist. Using a simple quantitative model, we provide new insight in this phenomenon. We present data that show convincingly that for cells or droplets with diameters upwards of a few micrometers, shape deformations induce adsorption of proteins at their interface even at moderate flow rates.
    Generalized surface momentum balances for the analysis of surface dilatational data
    Sagis, L.M.C. - \ 2013
    The European Physical Journal. Special Topics 222 (2013)1. - ISSN 1951-6355 - p. 31 - 38.
    in-water emulsions - interfacial permeability - superficial viscosity - bending rigidity - lipid-bilayers - fluid - dynamics - liquid - microbubbles - mixtures
    Dilatational rheological properties of interfaces are often determined using drop tensiometers, in which the interface of the droplet is subjected to oscillatory area changes. A dynamic surface tension is determined either by image analysis of the droplet profile or by measuring the capillary pressure. Both analysis modes tend to use the Young-Laplace equation for determining the dynamic surface tension. For complex fluid-fluid interfaces there is experimental evidence that this equation does not describe the response of the interface to deformations adequately. Generalizations of this equation are available, and in this comment we will discuss these generalizations, and the conditions for which they reduce to the Young-Laplace equation.
    Dynamics of encapsulation and controlled release systems bases on water-in-water emulsions: Liposomes and polymersomes
    Sagis, L.M.C. - \ 2009
    Physica A 388 (2009)13. - ISSN 0378-4371 - p. 2579 - 2587.
    interfacial permeability - shear-flow - vesicles - deformation - relaxation - membranes - behavior - bilayers
    The deformation relaxation behavior of two types of vesicles, liposomes and polymersomes, was investigated using a general nonequilibrium thermodynamics theory based on the interfacial transport phenomena (ITP) formalism. Liposomes and polymersomes are limiting cases of this theory with respect to rheological behavior of the interfaces. They represent respectively viscous, and viscoelastic surface behavior. We have determined the longest relaxation time for a small perturbation of the interfaces for both these limiting cases. Parameter maps were calculated which can be used to determine when surface tension, bending rigidity, spontaneous curvature, interfacial permeability, or surface rheology dominate the response of the vesicles. In these systems up to nine different scaling regimes were identified for the relaxation time of a deformation with droplet size, with scaling exponent n ranging from 0 to 4
    Dynamics of Encapsulation and Controlled Release Systems Based on Water-in-Water Emulsions: Negligible Surface Rheology
    Sagis, L.M.C. - \ 2008
    The Journal of Physical Chemistry Part B: Condensed Matter, Materials, Surfaces, Interfaces & Biophysical 112 (2008)43. - ISSN 1520-6106 - p. 13503 - 13508.
    interfacial permeability - microemulsion droplets - fluctuations - relaxation - mixtures - shape
    A nonequilibrium thermodynamic model based on the interfacial transport phenomena (ITP) formalism was used to study deformation¿relaxation behavior of water-in-water emulsions. The ITP formalism allows us to describe all water-in-water emulsions with one single theory. Phase-separated biopolymer solutions, hydrogel beads, liposomes, polymersomes, colloidosomes, and aqueous polymer microcapsules are all limiting cases of this general theory with respect to rheological behavior of the bulk phases and interfaces. Here we have studied two limiting cases of the general theory, with negligible surface rheology: phase-separated biopolymer solutions and hydrogel beads. We have determined the longest relaxation time for a small perturbation of the interfaces in these systems. Parameter maps were calculated which can be used to determine when surface tension, bending rigidity, permeability, and bulk viscoelasticity dominate the response of a droplet or gel bead. In phase-separated biopolymer solutions and dispersions of hydrogel beads six different scaling regimes can be identified for the relaxation time of a deformation. Hydrogel beads may also have a damped oscillatory response to a deformation. The results presented here provide new insight into the complex dynamics of water-in-water emulsions and also suggest new experiments that can be used to characterize the interfacial properties of these systems.
    Dynamics of controlled release systems based on water-in-water emulsions: A general theory
    Sagis, L.M.C. - \ 2008
    Journal of Controlled Release 131 (2008)1. - ISSN 0168-3659 - p. 5 - 13.
    common line motion - simple shear-flow - interfacial permeability - mechanical-properties - bending rigidity - surface-tension - lipid-bilayers - spinning drop - drug-release - vesicles
    Phase-separated biopolymer solutions, and aqueous dispersions of hydrogel beads, liposomes, polymersomes, aqueous polymer microcapsules, and colloidosomes are all examples of water-in-water emulsions. These systems can be used for encapsulation and controlled release purposes, in for example food or pharmaceutical applications. The stress-deformation behavior of the droplets in these systems is very complex, and affected by mass transfer across the interface. The relaxation time of a deformation of a droplet may depend on interfacial properties such as surface tension, bending rigidity, spontaneous curvature, permeability, and interfacial viscoelasticity. It also depends on bulk viscoelasticity and composition. A non-equilibrium thermodynamic model is developed for the dynamic behavior of these systems, which incorporates all these parameters, and is based on the interfacial transport phenomena (ITP) formalism. The ITP formalism allows us to describe all water-in-water emulsions with one general theory. Phase-separated biopolymer solutions, and dispersions of hydrogel beads, liposomes, polymersomes, polymer microcapsules, and colloidosomes are basically limiting cases of this general theory with respect to bulk and interfacial rheological behavior.
    Nonequilibrium Thermodynamic Model of Water-in-Water Emulsions
    Sagis, L.M.C. - \ 2007
    The Journal of Physical Chemistry Part C: Nanomaterials and Interfaces 111 (2007)7. - ISSN 1932-7447 - p. 3139 - 3145.
    interfacial permeability - bending rigidity - biopolymer - deformation - mixtures
    The dynamic behavior of highly permeable interfaces in phase-separated biopolymer solutions, liposomes, polymersomes, and colloidosomes is investigated. Using nonequilibrium thermodynamics, an expression for the correlation function of the height of a flat interface is derived for a multicomponent system, incorporating the effects of mass transfer across the interface. In addition, an expression is derived for the relaxation time of the height correlation function. This relaxation time is calculated 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 fluctuations of the interface. At small values for the amplitude, the relaxation of fluctuations is completely dominated by the permeability of the interface. At high values for the amplitude, the relaxation is dominated by the viscosities and densities of the bulk phases. In this regime, the long-time limit of the height correlation function shows multiexponential decay. The existence of such a multiexponential response was confirmed by recent experiments (Biomacomolecules 2006, 7, 2224). The crossover length between permeability- and viscosity-dominated relaxation is in the range of 0.1-50 µm.
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