| 1. |
- Balestra, G., et al.
(författare)
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Viscous Taylor droplets in axisymmetric and planar tubes : from Bretherton’s theory to empirical models
- 2018
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Ingår i: Microfluidics and Nanofluidics. - : Springer Verlag. - 1613-4982 .- 1613-4990. ; 22:6
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study is to derive accurate models for quantities characterizing the dynamics of droplets of non-vanishing viscosity in capillaries. In particular, we propose models for the uniform-film thickness separating the droplet from the tube walls, for the droplet front and rear curvatures and pressure jumps, and for the droplet velocity in a range of capillary numbers, Ca, from 10 - 4 to 1 and inner-to-outer viscosity ratios, λ, from 0, i.e. a bubble, to high-viscosity droplets. Theoretical asymptotic results obtained in the limit of small capillary number are combined with accurate numerical simulations at larger Ca. With these models at hand, we can compute the pressure drop induced by the droplet. The film thickness at low capillary numbers (Ca< 10 - 3) agrees well with Bretherton’s scaling for bubbles as long as λ< 1. For larger viscosity ratios, the film thickness increases monotonically, before saturating for λ> 10 3 to a value 2 2 / 3 times larger than the film thickness of a bubble. At larger capillary numbers, the film thickness follows the rational function proposed by Aussillous and Quéré (Phys Fluids 12(10):2367–2371, 2000) for bubbles, with a fitting coefficient which is viscosity-ratio dependent. This coefficient modifies the value to which the film thickness saturates at large capillary numbers. The velocity of the droplet is found to be strongly dependent on the capillary number and viscosity ratio. We also show that the normal viscous stresses at the front and rear caps of the droplets cannot be neglected when calculating the pressure drop for Ca> 10 - 3.
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| 2. |
- Bengtsson, Katarina, 1985-, et al.
(författare)
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A clip-on electroosmotic pump for oscillating flow in microfluidic cell culture devices
- 2018
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Ingår i: Microfluidics and Nanofluidics. - : Springer Berlin/Heidelberg. - 1613-4982 .- 1613-4990. ; 22:3
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Tidskriftsartikel (refereegranskat)abstract
- Recent advances in microfluidic devices put a high demand on small, robust and reliable pumps suitable for high-throughput applications. Here we demonstrate a compact, low-cost, directly attachable (clip-on) electroosmotic pump that couples with standard Luer connectors on a microfluidic device. The pump is easy to make and consists of a porous polycarbonate membrane and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) electrodes. The soft electrode and membrane materials make it possible to incorporate the pump into a standard syringe filter holder, which in turn can be attached to commercial chips. The pump is less than half the size of the microscope slide used for many commercial lab-on-a-chip devices, meaning that these pumps can be used to control fluid flow in individual reactors in highly parallelized chemistry and biology experiments. Flow rates at various electric current and device dimensions are reported. We demonstrate the feasibility and safety of the pump for biological experiments by exposing endothelial cells to oscillating shear stress (up to 5 dyn/cm2) and by controlling the movement of both micro- and macroparticles, generating steady or oscillatory flow rates up to ± 400 μL/min.
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| 3. |
- Bengtsson, Katarina, et al.
(författare)
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A large-area, all-plastic, flexible electroosmotic pump
- 2017
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Ingår i: Microfluidics and Nanofluidics. - : SPRINGER HEIDELBERG. - 1613-4982 .- 1613-4990. ; 21:12
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Tidskriftsartikel (refereegranskat)abstract
- A large-area, fabric-like pump would potentially have applications, for example, in controlling water transport through a garment, such as a rain jacket, regardless of the external temperature and humidity. This paper presents an all-plastic, flexible electroosmotic pump, constructed from commercially available materials: A polycarbonate membrane combined with the electrochemically active polymer poly(3,4-ethylenedioxythiophene) polystyrene sulfonate that actively transports water using an electric potential that can be supplied by a small battery. By using electrochemically active polymer electrodes instead of metal electrodes, the electrochemical reaction that drives flow avoids the oxygen and hydrogen gas production or pH changes associated with water electrolysis. We observe a water mass flux up to 23 mg min(-1) per cm(2) polycarbonate membrane (porosity 10-15%), at an applied potential of 5 V, and a limiting operating pressure of 0.3 kPa V-1, similar to previously reported membrane-based electroosmotic pumps.
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| 4. |
- Cerbelli, Stefano, et al.
(författare)
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Effective dispersion and separation resolution in continuous particle fractionation
- 2015
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Ingår i: Microfluidics and Nanofluidics. - : Springer Science and Business Media LLC. - 1613-4982 .- 1613-4990. ; 19:5, s. 1035-1046
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Tidskriftsartikel (refereegranskat)abstract
- Theoretical models and experiments suggest that the transport of suspended particles in microfluidics-based sorting devices can be modeled by a two-dimensional effective advection-diffusion process characterized by constant average velocity, $$\mathbf {W}$$W, and a typically anisotropic dispersion tensor, $$\mathbb {D}$$D, whose principal axes are slanted with respect to the direction of the effective velocity. We derive a closed-form expression connecting the effective transport parameters to separation resolution in continuous particle fractionation. We show that the variance of the steady-state particle concentration profile at an arbitrary cross-section of the device depends upon a scalar dispersion parameter, $$D_\mathrm{eff}$$Deff, which is primarily controlled by the projection of the dispersion tensor onto the direction orthogonal to $$\mathbf {W}$$W. Numerical simulations of particle transport in a Deterministic Lateral Displacement device, here used as a benchmark to illustrate the practical use of the effective transport approach, indicate that sustained dispersion regimes typically arise, where the dispersion parameter $$\mathcal {D}_\mathrm{eff}$$Deff can be orders of magnitude larger than the bare particle diffusivity.
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| 5. |
- Cohen, Céline, et al.
(författare)
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Parallelised production of fine and calibrated emulsions by coupling flow-focusing technique and partial wetting phenomenon
- 2014
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Ingår i: Microfluidics and Nanofluidics. - : Springer. - 1613-4982 .- 1613-4990. ; 17:5, s. 959-966
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Tidskriftsartikel (refereegranskat)abstract
- The capacity of microfluidic technology to fabricate monodisperse emulsion droplets is well established. Parallelisation of droplet production is a prerequisite for using such an approach for making high-quality materials for either fundamental or industrial applications where product quantity matters. Here, we investigate the emulsification efficiency of parallelised drop generators based on a flow-focusing geometry when incorporating the role of partial wetting in order to make emulsion droplets with a diameter below 10 μm. Confinement intrinsically encountered in microsystems intensifies the role played by interfaces between liquids and solids. We thus take advantage of partial wetting to enhance the maximum confinement accessible due to liquid flow focusing. We compare the performances brought by partial wetting to more established routes such as step emulsification. We show that the step configuration and the partial wetting regime are both well suited for being parallelised and thus open the way to the production of fine and calibrated emulsions for further applications. Finally, this new route of emulsification that exploits partial wetting between the fluids and the channel walls opens possibilities to the formation of substantially smaller droplets, as required in many fields of application.
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| 6. |
- Do-Quang, Minh, et al.
(författare)
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Fluid dynamic behavior of dispensing small droplets through a thin liquid film
- 2010
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Ingår i: Microfluidics and Nanofluidics. - : Springer Science and Business Media LLC. - 1613-4982 .- 1613-4990. ; 9:2-3, s. 303-311
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a technology for dispensing droplets through thin liquid layers. The system consists of a free liquid film, which is suspended in a frame and positioned in front of a piezoelectric printhead. A droplet, generated by the printhead, merges with the film, but due to its momentum, passes through and forms a droplet that separates on the other side and continues its flight. The technology allows the dispensing, mixing and ejecting of picolitre liquid samples in a single step. This paper overviews the concept, potential applications, experiments, results and a numerical model. The experimental work includes studying the flight of ink droplets, which ejected from an inkjet print head, fly through a free ink film, suspended in a frame and positioned in front of the printhead. We experimentally observed that the minimum velocity required for the 80 pl droplets to fly through the 75 ± 24 lm thick ink film was of 6.6 m s-1. We also present a numerical simulation of the passage of liquid droplets through a liquid film. The numerical results for different initial speeds of droplets and their shapes are taken into account. We observed that during the droplet-film interaction, the surface energy is partially converted to kinetic energy, and this, together with the impact time, helps the droplets penetrate the film. The model includes the Navier- Stokes equations with continuum-surface-tension force derived from the phase-field/Cahn-Hilliard equation. This system allows us to simulate the motion of a free surface in the presence of surface tension during merging, mixing and ejection of droplets. The influence of dispensing conditions was studied and it was found that the residual velocity of droplets after their passage through the thin liquid film well matches the measured velocity from the experiment.
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| 7. |
- Fornell, Anna, et al.
(författare)
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Intra-droplet acoustic particle focusing : simulations and experimental observations
- 2018
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Ingår i: Microfluidics and Nanofluidics. - : Springer Berlin/Heidelberg. - 1613-4982 .- 1613-4990. ; 22:75
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this paper is to study resonance conditions for acoustic particle focusing inside droplets in two-phase microfluidic systems. A bulk acoustic wave microfluidic chip was designed and fabricated for focusing microparticles inside aqueous droplets (plugs) surrounded by a continuous oil phase in a 380-μm-wide channel. The quality of the acoustic particle focusing was investigated by considering the influence of the acoustic properties of the continuous phase in relation to the dispersed phase. To simulate the system and study the acoustic radiation force on the particles inside droplets, a simplified 3D model was used. The resonance conditions and focusing quality were studied for two different cases: (1) the dispersed and continuous phases were acoustically mismatched (water droplets in fluorinated oil) and (2) the dispersed and continuous phases were acoustically matched (water droplets in olive oil). Experimentally, we observed poor acoustic particle focusing inside droplets surrounded by fluorinated oil while good focusing was observed in droplets surrounded by olive oil. The experimental results are supported qualitatively by our simulations. These show that the acoustic properties (density and compressibility) of the dispersed and continuous phases must be matched to generate a strong and homogeneous acoustic field inside the droplet that is suitable for high-quality intra-droplet acoustic particle focusing.
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| 8. |
- Garofalo, Fabio
(författare)
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On the methodologies for the assessment of the impact of parameters in acoustophoretic separation devices
- 2019
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Ingår i: Microfluidics and Nanofluidics. - : Springer Science and Business Media LLC. - 1613-4982 .- 1613-4990. ; 23:7
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Tidskriftsartikel (refereegranskat)abstract
- In this communication, we reconcile the kinematic method illustrated by some authors (Yang et al. in Microfluid Nanofluid 22:44–56, 2018; Vitali et al. in RSC Adv 8:38955, 2018) in studying the impact of system and suspension parameters on acoustophoretic separations with the statistical method formerly proposed by Garofalo (Microfluid Nanofluid 18(3):367–382, 2014a; ASME 2014 3rd global congress on nanoengineering for medicine and biology NEMB2014-93092, 2014b. https://www.researchgate.net/publication/259962346_Free-flow_acoustofluidic_devices_kinematics_cross-sectional_dispersion_and_particle_ensemble_correlations_Presentation) and lately extended to particle populations by the same author (Garofalo in CBMS the 14th conference on acoustofluidics, San Diego (CA), August 28–29, 2017, 2017. https://www.researchgate.net/publication/259962346_Free-flow_acoustofluidic_devices_kinematics_cross-sectional_dispersion_and_particle_ensemble_correlations_Presentation; Quantifying acoustophoretic separation of microparticle populations by mean-and-covariance dynamics for Gaussians in mixture models, 2018. arXiv:1802.09790). The connection between these two methods is established by (1) reinterpreting the kinematic method in terms of tangent space dynamics, and (2) transforming the dynamics in the tangent space into the dynamics of the area elements. The dynamics of the area elements is equivalent to the dynamics of the covariance matrix derived by moment analysis and associated with the dispersion problem during microparticle acoustophoresis. The similarities and the differences between the kinematic based method and the stochastic method proposed by the present author are illustrated and discussed in the light of the numerical results for a prototypical model of acoustophoretic separation.
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| 9. |
- Garofalo, Fabio, et al.
(författare)
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Statistic estimation of cell compressibility based on acoustophoretic separation data
- 2020
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Ingår i: Microfluidics and Nanofluidics. - : Springer Science and Business Media LLC. - 1613-4982 .- 1613-4990. ; 24:8
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Tidskriftsartikel (refereegranskat)abstract
- We present a new experimental method that measures the compressibility of phenotype-specific cell populations. This is done by performing statistical analysis of the cell counts from the outlets of an acoustophoresis chip as a function of the increasing actuator voltage (i.e. acoustic energy density) during acoustophoretic separation. The theoretical separation performance curve, henceforth, Side-Stream Recovery (SSR), vs the piezo-actuator voltage (V) is derived by moment analysis of a one-dimensional model of acoustophoresis separation, accounting for distributions of the cell or microparticle properties and the system parameters (hydrodynamics, radiation force, drag enhancement, and acoustic streaming). The acoustophoretic device is calibrated with polymer microbeads of known properties by fitting the experimental SSR with the theoretical SSR , in which the acoustic energy density is considered proportional to the squared voltage, i.e. Eac=αV2. The fitting parameter α for the calibration procedure is the device effectivity, reflecting the efficiency in performing acoustophoretic microparticle displacement. Once calibrated, the compressibility of unknown cells is estimated by fitting experimental SSR cell data points with the theoretical SSR curve. In this procedure, the microparticle compressibility is the fitting parameter. The method is applied to estimate the compressibility of a variety of cell populations showing its utility in terms of rapid analysis and need for minute sample amounts.
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| 10. |
- Gong, Shengjie, et al.
(författare)
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Diagnostic techniques for the dynamics of a thin liquid film under forced flow and evaporating conditions
- 2010
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Ingår i: MICROFLUID NANOFLUID. - : Springer Science and Business Media LLC. - 1613-4982. ; 9:6, s. 1077-1089
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Tidskriftsartikel (refereegranskat)abstract
- Motivated by quantification of micro-hydrodynamics of a thin liquid film which is present in industrial processes, such as spray cooling, heating (e.g., boiling with the macrolayer and the microlayer), coating, cleaning, and lubrication, we use micro-conductive probes and confocal optical sensors to measure the thickness and dynamic characteristics of a liquid film on a silicon wafer surface with or without heating. The simultaneous measurement on the same liquid film shows that the two techniques are in a good agreement with respect to accuracy, but the optical sensors have a much higher acquisition rate up to 30 kHz which is more suitable for rapid process. The optical sensors are therefore used to measure the instantaneous film thickness in an isothermal flow over a silicon wafer, obtaining the film thickness profile and the interfacial wave. The dynamic thickness of an evaporating film on a horizontal silicon wafer surface is also recorded by the optical sensor for the first time. The results indicate that the critical thickness initiating film instability on the silicon wafer is around 84 mu m at heat flux of similar to 56 kW/m(2). In general, the tests performed show that the confocal optical sensor is capable of measuring liquid film dynamics at various conditions, while the micro-conductive probe can be used to calibrate the optical sensor by simultaneous measurement of a film under quasi-steady state. The micro-experimental methods provide the solid platform for further investigation of the liquid film dynamics affected by physicochemical properties of the liquid and surfaces as well as thermal-hydraulic conditions.
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| 11. |
- Ogden, Sam, 1979-, et al.
(författare)
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Fluid behavior of supercritical carbon dioxide with water in a double-Y-channel microfluidic chip
- 2014
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Ingår i: Microfluidics and Nanofluidics. - : Springer Science and Business Media LLC. - 1613-4982 .- 1613-4990. ; 17:6, s. 1105-1112
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Tidskriftsartikel (refereegranskat)abstract
- The use of supercritical carbon dioxide (scCO(2)) as an apolar solvent has been known for decades. It offers a greener approach than, e.g., hexane or chloroform, when such solvents are needed. The use of scCO(2) in microsystems, however, has only recently started to attract attention. In microfluidics, the flow characteristics need to be known to be able to successfully design such components and systems. As supercritical fluids exhibit the exciting combination of low viscosity, high density, and high diffusion rates, the fluidic behavior is not directly transferrable from aqueous systems. In this paper, three flow regimes in the scCO(2)-liquid water two-phase microfluidic system have been mapped. The effect of both total flow rate and relative flow rate on the flow regime is evaluated. Furthermore, the droplet dynamics at the bifurcating exit channel are analyzed at different flow rates. Due to the low viscosity of scCO(2), segmented flows were observed even at fairly high flow rates. Furthermore, the carbon dioxide droplet behavior exhibited a clear dependence on both flow rate and droplet length.
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| 12. |
- Ogden, Sam, 1979-, et al.
(författare)
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Review on miniaturized paraffin phase change actuators, valves, and pumps
- 2014
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Ingår i: Microfluidics and Nanofluidics. - : Springer Science and Business Media LLC. - 1613-4982 .- 1613-4990. ; 17:1, s. 53-71
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Forskningsöversikt (refereegranskat)abstract
- During the last fifteen years, miniaturised paraffin actuation has evolved through the need of a simple actuation principle, still able to deliver large strokes and high actuation forces at small scales. This is achieved by the large and rather incompressible volume expansion associated with the solid-to-liquid phase transition of paraffin. The common approach has been to encapsulate the paraffin by a stiff surrounding that directs the volume expansion towards a flexible membrane, which deflects in a directed stroke. However, a number of alternative methods have also been used in the literature. The most common applications to this date have been switches, positioning actuators, and microfluidic valves and pumps. This review will treat the historical background, as well as the fundamentals in paraffin actuation, including material properties of paraffin. Besides reviewing the three major groups of paraffin actuator applications; actuators, valves, and pumps, the modelling done on paraffin actuation will be explored. Furthermore, a section focusing on fabrication of paraffin microactuators is also included. The review ends with conclusions and outlook of the field, identifying unexplored potential of paraffin actuation.
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| 13. |
- Ohlsson, Gabriel, 1982, et al.
(författare)
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A miniaturized flow reaction chamber for use in combination with QCM-D sensing
- 2010
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Ingår i: Microfluidics and Nanofluidics. - : Springer Science and Business Media LLC. - 1613-4990 .- 1613-4982. ; 9:4-5, s. 705-716
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Tidskriftsartikel (refereegranskat)abstract
- A miniaturized flow chamber for quartz crystal microbalance with dissipation monitoring (QCM-D) has been developed. The main purpose was to reduce the total liquid sample consumption during an experiment, but also to gain advantages with respect to kinetics and mass transport by reducing the boundary diffusion layer. The bottom of the flow chamber is a QCM-D sensor surface, on which a polydimethylsiloxane spacer ring, fabricated onto a poly(methyl methacrylate) lid, is placed symmetrically around the QCM-D electrode (diameter similar to 10 mm). The spacer ring defines the inner chamber height (typically 40-50 mu m) and provides sealing. Through the lid, there are inlet and outlet channels. The typical chamber volume is in the range of 2.5-3.5 mu l (with a 10 mu l dead volume). In flow mode, we have operated the cell at flow rates of 6-50 mu l/min, i.e., volume turnovers of 2-17 per min. As a model system, to test the microcell, the formation of supported phospholipid bilayers on a SiO2 surface was studied. For comparison, the same process was studied in a commercially available QCM-D equipment with significantly larger total volume (by a factor of 20). The decrease in effective sample consumption to produce a bilayer on the sensor surface in the chamber was approximately proportional to the decrease in chamber volume. Smaller volume also reduced the liquid exchange time. Potential improvements of the chamber include further optimization of the flow profile and, in addition, further miniaturization by decreasing the chamber height and the sensor radius.
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| 14. |
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| 15. |
- Oko, Asaf, et al.
(författare)
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Infiltration and dimensional scaling of inkjet droplets on thick isotropic porous materials
- 2014
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Ingår i: Microfluidics and Nanofluidics. - : Springer Science and Business Media LLC. - 1613-4982 .- 1613-4990. ; 17:2, s. 413-422
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Tidskriftsartikel (refereegranskat)abstract
- We study the imbibition of picoliter (pL)-sized inkjet droplets on controlled pore glass membranes (CPG), as a suitable model for isotropic three-dimensional porous materials. We do so using a variety of liquids, i.e., water, formamide and diiodomethane, and measure the evolution of the imbibition process using high-speed digital imaging. Here, experiments were conducted on 2-280 nm CPG membranes with drops with initial volumes ranging from 100 to 600 pL. We derive scaling laws for imbibition through dimensional analysis and advance the argument that the rate of absorption is related to two-dimensionless groups where v(t) is the imbibed volume, as determined from experiments, t is the time, v (tot) the total liquid volume, the porosity, mu the liquid viscosity, k the permeability, and p (c) the Laplace capillary pressure. We show this scaling to well describe the system at intermediate T values and report that V alpha T-0.8.
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| 16. |
- Pardon, Gaspard, 1983-, et al.
(författare)
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Rapid mold-free manufacturing of microfluidic devices with robust and spatially directed surface modifications
- 2014
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Ingår i: Microfluidics and Nanofluidics. - : Springer Berlin/Heidelberg. - 1613-4982 .- 1613-4990. ; 17:4, s. 773-779
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Tidskriftsartikel (refereegranskat)abstract
- A new method that allows for mold-free, rapid and easy-to-use proto- typing of micro uidic devices comprising channels, access holes and surface modied patterns, is presented. The innovative method is based on direct photolithographic patterning of an o-stoichiometry thiol-ene (OSTE) polymer formulation, tailor-made for photolithography, which oers unprecedented spatial resolution and allow for ecient, robust and reliable, room temperature surface modication and glue-free, covalent room temperature bonding. This mold-free process does not require cleanroom equipment and therefore allows for rapid, i.e. less than one hour, design-fabricate-test cycles, using a material suited for larger scale production. The excellent photolithographic properties of this new OSTE formulation allow for high-resolution patterning in hundreds of micrometers thick layers, 200 m thick in this work. Moreover, we demonstrate robust (covalent) and spatially controlled modication of the microchannel surfaces with a contact angle of 76 degrees to hydrophobic/hydrophilic areas with contact angles of 102 and 43 degrees, respectively.
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| 17. |
- Pihl, Maria, 1978, et al.
(författare)
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Effect of patchwise slip on fluid flow
- 2014
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Ingår i: Microfluidics and Nanofluidics. - : Springer Science and Business Media LLC. - 1613-4982 .- 1613-4990. ; 17:2, s. 341-347
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we show that large connected slip patches (hydrophobic patches) are a necessity to induce macroscopic slip effects of water flow in microchannels. For this purpose, the 2D fluid flow between a planar stationary surface with alternating stick and slip patches and a parallel planar surface moving with a constant relative velocity has been studied by computer simulations based on Navier-Stokes equations. A slip patch is defined as the slipping length in a 2D system or a slip area of the surface in a 3D system. The simulations reveal that the ratio (size of each slip patch)/(distance between the two parallel interfaces) has profound effect on the viscous stress on the moving surface when this ratio is around and above one. However, when the ratio is much below one, the effect of the slip patches are minor, even if the area fraction of slip patches are higher than 50 %. Obviously, the stick patches adjacent to the slip patches act as effective barriers, preventing the fluid velocity to increase near the surface with alternating stick and slip patches. The obtained results are scalable and applicable on all length scales, with an exception for narrow channels in the subnano regime, i.e. < 1 nm where specific effects as the atomistic composition and the nanostructure of the wall as well as the interactions between the wall and the water molecules have an effect.
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| 18. |
- Qian, Jin yuan, et al.
(författare)
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A comprehensive review on liquid–liquid two-phase flow in microchannel : flow pattern and mass transfer
- 2019
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Ingår i: Microfluidics and Nanofluidics. - : Springer Science and Business Media LLC. - 1613-4982 .- 1613-4990. ; 23:10
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Forskningsöversikt (refereegranskat)abstract
- Liquid–liquid two-phase flow in microchannel is very common in micro-chemical and micro-biological system, etc. Deep understanding of the liquid–liquid two-phase flow mechanisms and mass transfer in microchannel can promote industrial applications significantly. To summarize the recent research progress on the liquid–liquid two-phase flow in microchannel, this paper collects research work about this topic, especially focusing on flow pattern and mass transfer. To begin with, flow patterns observed in various conditions are identified and factors which influence the flow patterns are analyzed. Then, mass transfer in liquid–liquid two-phase flow is discussed, especially the mass transfer during droplet flow, with both experiments and simulations. Furthermore, energy dissipation involved in liquid–liquid two-phase flow in microchannel is also briefly discussed. Finally, future needs are proposed for extending the researches on liquid–liquid two-phase flow and enlarging its application fields.
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| 19. |
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| 20. |
- Valijam, Shayan, et al.
(författare)
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Design of a low-voltage dielectrophoresis lab-on-the chip to separate tumor and blood cells
- 2023
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Ingår i: Microfluidics and Nanofluidics. - : Springer Berlin/Heidelberg. - 1613-4982 .- 1613-4990. ; 27:3
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we design and propose a compact label-free microfluidic lab-on-a-chip device to separate circulating tumor cells (CTCs) from red blood cells (RBCs) at low voltage to minimize cell damage. With the aim of developing a mm-long device to perform cell separation, we used 3D finite element simulation modeling and investigated separation efficiency for different electrode configurations, electrode shapes, and channel heights. Our results show that configuring the electrodes as two arrays, consisting of only five pairs of top and bottom planar electrodes shifted relative to each other and energized with ± 6 V at 70 kHz, generates sufficient non-uniform electric fields to separate CTCs and RBCs in a 2 mm long channel. The advantage of the proposed design is the simplicity of the electrode arrangement and that the electrodes do not cover the central part of the channel, thus allowing for brightfield imaging of the channel. In addition, the low voltage needed and the 50 µm high channel reduce the Joule heating effect and improve the device's separation and throughput efficiency. We suggest that the proposed design would be effective for separating CTCs and RBCs and, thus, used as a device for the early detection of CTCs.
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| 21. |
- van der Wijngaart, Wouter
(författare)
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Capillary pumps with constant flow rate
- 2014
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Ingår i: Microfluidics and Nanofluidics. - Springer : Springer Science and Business Media LLC. - 1613-4982 .- 1613-4990. ; 16:5, s. 829-837
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Tidskriftsartikel (refereegranskat)abstract
- This paper unambiguously derives, ab initio starting from the Navier–Stokes and Laplace equations, the geometric parameters defining capillary pumps (CPs) with rectangular cross section with constant volumetric flow rate and steady velocity profile. The parametric formulation of the channel shape is derived using Taylor series approximations of the capillary pressure and the hydrodynamic flow resistance with negligible error. First, the design parameters are derived for a CP consisting of a single channel and illustrated with an example. Thereafter, the design parameters for multichannel and for micropillar array CPs are derived. Finally, the design of CPs for multistep constant flow rates derived and those for arbitrarily varying flow rates are discussed.
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| 22. |
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| 23. |
- Xu, Wenchao, et al.
(författare)
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Viscosity-difference-induced asymmetric selective focusing for large stroke particle separation
- 2016
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Ingår i: Microfluidics and Nanofluidics. - : Springer Science and Business Media LLC. - 1613-4982 .- 1613-4990. ; 20:9
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Tidskriftsartikel (refereegranskat)abstract
- We developed a new approach for particle separation by introducing viscosity difference of the sheath flows to form an asymmetric focusing of sample particle flow. This approach relies on the high-velocity gradient in the asymmetric focusing of the particle flow to generate a lift force, which plays a dominated role in the particle separation. The larger particles migrate away from the original streamline to the side of the higher relative velocity, while the smaller particles remain close to the streamline. Under high-viscosity (glycerol-water solution) and low-viscosity (PBS) sheath flows, a significant large stroke separation between the smaller (1.0 mu m) and larger (9.9 mu m) particles was achieved in a sample microfluidic device. We demonstrate that the flow rate and the viscosity difference of the sheath flows have an impact on the interval distance of the particle separation that affects the collected purity and on the focusing distribution of the smaller particles that affects the collected concentration. The interval distance of 293 mu m (relative to the channel width: 0.281) and the focusing distribution of 112 mu m (relative to the channel width: 0.107) were obtained in the 1042-mu m-width separation area of the device. This separation method proposed in our work can potentially be applied to biological and medical applications due to the wide interval distance and the narrow focusing distribution of the particle separation, by easy manufacturing in a simple device.
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| 24. |
- Sachs, Sebastian, et al.
(författare)
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On the behavior of prolate spheroids in a standing surface acoustic wave field
- 2023
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Ingår i: Microfluidics and Nanofluidics. - 1613-4982. ; 27:12
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Tidskriftsartikel (refereegranskat)abstract
- The active manipulation of particle and cell trajectories in fluids by high-frequency standing surface acoustic waves (sSAW) allows to separate particles and cells systematically depending on their size and acoustic contrast. However, process technologies and biomedical applications usually operate with non-spherical particles, for which the prediction of acoustic forces is highly challenging and remains a subject of ongoing research. In this study, the dynamical behavior of prolate spheroids exposed to a three-dimensional acoustic field with multiple pressure nodes along the channel width is examined. Optical measurements reveal an alignment of the particles orthogonal to the pressure nodes of the sSAW, which has not been reported in literature so far. The dynamical behavior of the particles is analyzed under controlled initial conditions for various motion patterns by imposing a phase shift on the sSAW. To gain detailed understanding of the particle dynamics, a three-dimensional numerical model is developed to predict the acoustic force and torque acting on a prolate spheroid. Considering the acoustically induced streaming around the particle, the numerical results are in excellent agreement with experimental findings. Using the proposed numerical model, a dependence of the acoustic force on the particle shape is found in relation to the acoustic impedance of the channel ceiling. Hence, the numerical model presented herein promises high progress for the design of separation devices utilizing sSAW, exploiting an additional separation criterion based on the particle shape.
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