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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    Partitioned EDGE devices for high throughput production of monodisperse emulsion droplets with two distinct sizes
    Sahin, S. ; Schroën, C.G.P.H. - \ 2015
    Lab on a Chip 15 (2015). - ISSN 1473-0197 - p. 2486 - 2495.
    flow membrane emulsification - microchannel emulsification - generation - dynamics - model - geometries - parallel
    We present a novel microfluidic EDGE (Edge based Droplet GEneration) device with regularly spaced micron-sized partitions, which is aimed at upscaling of o/w emulsion preparation. By this means, remarkably higher pressure stability was obtained, and two orders of magnitude higher droplet formation frequency was achieved compared to regular EDGE devices. Interestingly, we observed two different monodisperse droplet formation regimes for plateaus that were 2 micrometres in height, and to the best of our knowledge, no other microfluidic device has this ability. The average diameters of the droplets were 9 and 28 µm, both with a coefficient of variation (CV) below 5%. Based on the experimental throughput and a plausible mass parallelization scenario, the amount of hexadecane that can be emulsified is estimated to be between 6 and 25 m3 m-2 h-1 depending on the required droplet size. With its high throughput potential and ability to produce uniform droplets of two different sizes, the partitioned EDGE device is promising for industrial emulsion production.
    Influence of the emulsion formulation in premix emulsification using packed beds
    Nazir, A. ; Boom, R.M. ; Schroën, C.G.P.H. - \ 2014
    Chemical Engineering Science 116 (2014). - ISSN 0009-2509 - p. 547 - 557.
    in-water emulsions - droplet break-up - membrane emulsification - multiple emulsions - microchannel emulsification - interfacial-tension - drug-delivery - static mixers - homogenization - surfactant
    Premix emulsification was investigated using packed beds consisting of micron-sized glassbeads, a system that avoids fouling issues, unlike traditional premix membrane emulsification. The effects of emulsion formulation were investigated, most notably the viscosity and the surfactant. The dropletsize was reduced by increased shea rstress in the emulsion. This was stronger at low viscosity ratios than at high ratios. As expected the flux was proportional to the overall emulsion viscosity, and emulsions with small droplet size (Sauter mean droplet diameter o5 µm) could still be produced at up to 60% of dispersed phase provided that sufficient surfactant was available. More uniform emulsions(spanE0.75) were produced withTween-20(nonionic )and SDS(anionic) as surfactants than with CTAB (acationic surfactant), possibly due to acombination of a low equilibrium interfacia ltension and electrostatic attractions with the glass surface. Scaling relations were proposed taking into account all investigated product properties that can describe the dropletsize successfully.
    High throughput production of double emulsions using packed bed premix emulsification
    Sahin, S. ; Sawalha, H.I.M. ; Schroen, C.G.P.H. - \ 2014
    Food Research International 66 (2014). - ISSN 0963-9969 - p. 78 - 85.
    release rate profiles - in-water emulsions - multiple w/o/w emulsions - droplet break-up - membrane emulsification - microchannel emulsification - interfacial-tension - food applications - drug-delivery - nickel sieves
    We explored the potential of packed bed premix emulsification for homogenizing coarse food grade W/O/W emulsions, prepared with sunflower oil. Using packed beds with different glass bead sizes (30–90 µm) at different applied pressures (200–600 kPa), emulsions with reasonably uniform droplet size (span ~ 0.75) were produced successfully at high fluxes (100–800 m3 m- 2 h- 1). Sodium chloride was used as a release marker: after five homogenization cycles, the produced emulsions were found to retain almost all of their initial content (99%). As was previously found for single emulsions, the packed bed system proved to be effective in breaking up the W/O/W emulsion droplets, with droplet to pore size ratios as low as 0.3. Results were analysed through the pore Reynolds number, Rep, which characterizes the flow inside the packed bed, and were related back to the droplet break-up mechanisms occurring. At high Rep, droplet break-up was expected to be governed by shear forces while at low Rep, there is a shift from shear based to spontaneous droplet break-up.
    Effect of surface wettability on microfluidic EDGE emulsification
    Maan, A.A. ; Sahin, S. ; Mujawar, L.H. ; Boom, R.M. ; Schroen, C.G.P.H. - \ 2013
    Journal of Colloid and Interface Science 403 (2013). - ISSN 0021-9797 - p. 157 - 159.
    droplet formation - microchannel emulsification - emulsions - water
    The effect of wettability on microfluidic EDGE emulsification was investigated at dispersed phase contact angles between 90 and 160. The highest contact angle (160) produced monodispersed emulsions with droplet size 5.0 lm and coefficient of variation
    Droplet break-up mechanism in premix emulsification using
    Nazir, A. ; Boom, R.M. ; Schroën, C.G.P.H. - \ 2013
    Chemical Engineering Science 92 (2013). - ISSN 0009-2509 - p. 190 - 197.
    membrane emulsification - microchannel emulsification - multiple emulsions - glass membrane - static mixer - parameters
    Some emulsification techniques based on microstructures are known for the monodispersity of produced droplets, however, they lack in scalability. The techniques that are able to produce emulsions in larger amounts do not usually produce monodispersed droplets. We here report on a specific technique that has the potential to combine the best of both worlds: premix emulsification using a packed bed of differently sized glass beads (55, 65, 78 and 90 mm) supported by a metal sieve. The production of oil-in-water emulsions was targeted, and the process conditions especially related to internal structure of the porous media like interstitial void size and bed height were investigated. The Reynolds number, Re, was used to characterize the flow inside the packed bed consisting of asymmetric pores following a tortuous path inside the porous media. The void size and the flow velocity determined the droplet break-up. Two droplet break-up mechanisms were identified: either dominated by constriction (Reo40) or inertia (Re440). Droplets below 5 mm (droplet to void size ratioE0.2) could easily be produced; having relatively narrow droplet size distribution (droplet spanE0.75). The measured fluxes were comparable to the highest reported flux values for premix membrane emulsification studies. Statistically significant scaling relations were established for the studied process conditions.
    Monodispersed water-in-oil emulsions prepared with semi-metal microfluidic EDGE systems
    Maan, A.A. ; Schroën, C.G.P.H. ; Boom, R.M. - \ 2013
    Microfluidics and Nanofluidics 14 (2013)1. - ISSN 1613-4982 - p. 187 - 196.
    premix membrane emulsification - droplet formation - microchannel emulsification - microcapsules - devices
    Monodispersed water-in-oil emulsions were prepared with EDGE (Edge based Droplet GEneration) systems, which generate many droplets simultaneously from one junction. The devices (with plateau height of 1.0 µm) were coated with Cu and CuNi having the same hydrophobicity but different surface roughness. Emulsification was performed by using water as dispersed phase and oils with different viscosities (hexadecane, decane, hexane and sunflower oil) as continuous phases; lecithin, polyglycerol polyricinoleate (PGPR) and span80 were used as emulsifiers. The roughness affected the emulsification behaviour significantly. The smoother Cu surface exhibited droplet formation over the entire length of the droplet formation unit, while the rougher CuNi surface showed non-uniform filling of the plateau and much lower droplet formation frequency. In spite of this different behaviour, monodispersed droplets (CV
    High-throughput premix membrane emulsification using nickel sieves having straight-through pores
    Nazir, A. ; Schroën, C.G.P.H. ; Boom, R.M. - \ 2011
    Journal of Membrane Science 383 (2011)1-2. - ISSN 0376-7388 - p. 116 - 123.
    microchannel emulsification - multiple emulsions - break-up - droplets - viscosity - systems - flow - homogenization - dispersions - dynamics
    We report on the use of nickel sieves, having a uniform pore size (typically 10 µm × 300 µm), for (oil-in-water) premix emulsification at relatively low transmembrane pressures. The droplet break-up was found to be based on elongation and recompression of droplets typical of high-pressure homogenization. The dependence on the transmembrane pressure indicated at least partial turbulent conditions. In line with this, the transmembrane fluxes were very high, while a reasonable span (around 1) of the droplet size was found. There was no indication of fouling in the process, even after 5 passes, which indicates that the process is tolerant to product and conditions. A master curve was found for the Weber number as function of the transmembrane pressure normalized on the Laplace pressure of the emulsion before emulsification, which is helpful in further scale-up of this process
    High throughput vegetable oil-in-water emulsification with a high porosity micro-engineered membrane
    Wagdare, N.A. ; Marcelis, A.T.M. ; Ho, O.B. ; Boom, R.M. ; Rijn, C.J.M. van - \ 2010
    Journal of Membrane Science 347 (2010)1-2. - ISSN 0376-7388 - p. 1 - 7.
    droplet formation - microchannel emulsification - emulsions - stability - junction - surface - size
    Emulsification with high porosity micro-engineered membranes leads to stable emulsions with a low droplet span when, besides a surfactant in the continuous phase, an additional, suitable surfactant is used in the dispersed phase. This surfactant should exhibit relatively fast adsorption dynamics, which is more critical when the surfactant in the continuous phase has slower dynamics. Dispersed-phase fluxes of up to 92.5 x 10(-6) m(3)/m(2)s could be achieved, which is an order of magnitude higher than previously reported for SPG membrane-based cross-flow emulsification.
    Simultaneous formation of many droplets in a single microfluidic droplet formation unit
    Dijke, K.C. van; Veldhuis, G. ; Schroën, C.G.P.H. ; Boom, R.M. - \ 2010
    AIChE Journal 56 (2010)3. - ISSN 0001-1541 - p. 833 - 836.
    monodisperse emulsion droplets - microchannel emulsification - model - size
    EDGE emulsification for food-grade dispersions
    Dijke, K.C. van; Schroën, C.G.P.H. ; Padt, A. van der; Boom, R.M. - \ 2010
    Journal of Food Engineering 97 (2010)3. - ISSN 0260-8774 - p. 348 - 354.
    in-water emulsions - microchannel emulsification - interfacial-tension - droplet formation - membrane - array
    In this paper, we use the Edge-based Droplet GEneration (EDGE) emulsification method to produce food-grade emulsions (including double emulsions) and foams. This newly developed mild technology proved to be very stable and robust in the production of all these products. The products are made with food-grade components in an up-scaled micro device, which does not show any changes in time in wettability and fouling. The size of the droplets and bubbles is as needed for food stuffs. Air bubbles generated with EDGE were much larger than emulsion droplets, which could be explained through the viscosity ratio of the phases and changes in interfacial free energy caused by dynamic interfacial tension effects. In the outlook section of this paper, the obtained results are related to the dimensions of the devices, which are in a practically feasible range, also due to the simplicity of the EDGE structure and its operation. Preliminary estimations show that a 300L system can produce 1 m/h 4% (v/v) emulsion
    Parallelized edge-based droplet generation (EDGE) devices
    Dijke, K.C. van; Veldhuis, G. ; Schroën, C.G.P.H. ; Boom, R.M. - \ 2009
    Lab on a Chip 9 (2009). - ISSN 1473-0197 - p. 2824 - 2830.
    monodisperse emulsion droplets - microchannel emulsification - system - model - size
    We here report on three parallelized designs of the new edge-based droplet generation mechanism, which, unlike existing mechanisms, produces many equally sized droplets simultaneously at a single droplet formation unit. Operation of the scaled-out systems is straight forward; only the oil inlet pressure has to be controlled to let all the units produce oil droplets, given certain basic design constraints. For systems with a typical nozzle depth of 1.2 µm, the mean droplet diameter is 7.5 µm and the coefficient of variation is below 10%. The number of droplets that is formed per unit can easily be increased by increasing the length of the unit. The stable pressure range in which monodisperse droplets are formed can be extended by small adjustments to the design. Overall, the EDGE devices are simple in design and robust in use, making them suitable for massive outscaling
    Visualization of droplet break-up in pre-mix membrane emulsification using microfluidic devices
    Zwan, E.A. van der; Schroën, C.G.P.H. ; Dijke, K.C. van; Boom, R.M. - \ 2006
    Colloids and Surfaces. A: Physicochemical and Engineering Aspects 277 (2006)1-3. - ISSN 0927-7757 - p. 223 - 229.
    microchannel emulsification - emulsions - flow
    To investigate the break-up of emulsion droplets in pre-mix or dead-end membrane emulsification, a microscopic study was conducted in microfluidic devices. Channels with shapes such as constrictions, junctions, and combinations thereof representing ideal membrane structures where etched in silicon. Through these structures pre-mix emulsion droplets where pushed, which was recorded with high-speed video microscopy. Accumulation of droplets of the dispersed phase before and inside the pore network was found to occur under all conditions. Thus, the effective volume fraction of dispersed phase inside the pores is always high. In a brick-shaped pore structure, an optimum thickness of the layer was found. In these structures, channelling occurs below a critical pressure difference over the structure. In the channelling regime, isolated channels are active, effectively excluding action of branchings and junctions. We found three main categories of break-up mechanisms (snap-off due to localized shear, break-up due to interfacial tension effects, and break-up due to steric hindrance) and were able to quantify some. Break-up due to branchings and junctions do not seem to be essential for break-up to occur. It is, however, clear that the other phenomena (accumulation, channelling) can have major impact on the total behaviour of the system and should not be neglected.
    Preparation of double emulsions by membrane emulsification - a review
    Graaf, S. van der; Schroën, C.G.P.H. ; Boom, R.M. - \ 2005
    Journal of Membrane Science 251 (2005)1-2. - ISSN 0376-7388 - p. 7 - 15.
    seed oil microdroplets - arterial-injection chemotherapy - dynamic interfacial-tension - water multiple emulsions - hepatocellular-carcinoma - microchannel emulsification - w/o/w emulsion - droplet formation - aqueous vesicles - phase inversion
    Double emulsions have potential for the production of low calorie food products, encapsulation of medicines and other high value products. The main issue is the difficulty to efficiently produce double emulsions in a well controlled manner due to their shear sensitivity. In membrane emulsification only mild shear stresses are applied and it is therefore expected that this process is very suitable for the production of double emulsions. In this review an overview is given of the state of the art; the advantages and disadvantages of membrane emulsification in relation to the production of stable double emulsions are summarized and compared. Finally an outlook on further research in this field is given
    Status of cross-flow membrane emulsification and outlook for industrial application
    Gijsbertsen-Abrahamse, A.J. ; Padt, A. van der; Boom, R.M. - \ 2004
    Journal of Membrane Science 230 (2004)1-2. - ISSN 0376-7388 - p. 149 - 159.
    shirasu-porous-glass - in-water emulsions - microchannel emulsification - droplet formation - ceramic membranes - microspheres - size - pore
    Cross-flow membrane emulsification has great potential to produce monodisperse emulsions and emulsions with shear sensitive components. However, until now, only low disperse phase fluxes were obtained. A low flux maybe a limiting factor for emulsion production on a commercial scale. Therefore, the effects of membrane parameters on the disperse phase flux are estimated. Besides, the effects of these parameters on the droplet size and droplet size distribution are qualitatively described. Wetting properties, pore size and porosity mainly determine the droplet size (distribution). Membrane morphology largely determines the disperse phase flux. As an example, industrial-scale production of culinary cream was chosen to evaluate the required membrane area of different types of membranes: an SPG membrane, an alpha-Al2O3 membrane and a microsieve. Due to the totally different morphologies of these membranes, the fraction of active pores is I for a microsieve and is very low for the other membranes. The choice of the optimal membrane did not depend on the production strategy: either to produce large quantities or to produce monodisperse emulsions, the best suitable was a microsieve with an area requirement of around I m(2). In general, the total membrane resistance should be low to obtain a large disperse phase flux. In contrast, the membrane resistance should be high to obtain monodisperse emulsions when using membranes with a high porosity. (C) 2003 Elsevier B.V. All rights reserved.
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