Flow focusing with viscoelastic liquids

Derzsi, Ladislav; Kasprzyk, Marta; Plog, Jan Philip; Garstecki, Piotr

doi:10.1063/1.4817995

Cited by 58 publications

(44 citation statements)

References 58 publications

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“…Most of the attention was devoted to the formation of viscoelastic droplets carried by Newtonian continuous phases [11] and the effect of polymer molecular weight on filament thinning in flow-focusing devices [12,13]. The production of Newtonian droplets in a viscoelastic medium has instead been systematically investigated in the flow-focusing geometry to analyze the focusing effect due to the non-Newtonian continuous phase [14]. It was found that, with careful adjustment of the ratio of viscosities of the two immiscible liquids, viscoelasticity of the focusing liquid could help to lower the dispersion of the emulsions and to decrease the volume of the produced droplets.…”

Section: Introductionmentioning

confidence: 99%

Generation of Oil Droplets in a Non-Newtonian Liquid Using a Microfluidic T-Junction

et al. 2015

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Abstract:We have compared the formation of oil drops in Newtonian and non-Newtonian fluids in a T-junction microfluidic device. As Newtonian fluids, we used aqueous solutions of glycerol, while as non-Newtonian fluids we prepared aqueous solutions of xanthan, a stiff rod-like polysaccharide, which exhibit strong shear-thinning effects. In the squeezing regime, the formation of oil droplets in glycerol solutions is found to scale with the ratio of the dispersed flow rate to the continuous one and with the capillary number associated to the continuous phase. Switching to xanthan solutions does not seem to significantly alter the droplet formation process. Any quantitative difference with respect to the Newtonian liquid can be accounted for by a suitable choice of the capillary number, corresponding to an effective xanthan viscosity that depends on the flow rates. We have deduced ample variations in the viscosity, on the order of 10 and more, during normal operation conditions of the T-junction. This allowed estimating the actual shear rates experienced by the xanthan solutions, which go from tens to hundreds of s´1.

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Section: Introductionmentioning

confidence: 99%

Generation of Oil Droplets in a Non-Newtonian Liquid Using a Microfluidic T-Junction

et al. 2015

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“…The formation and the pinch-off mechanism of viscoelastic droplets in Newtonian continuous phases was investigated in various flowfocusing geometries by Steinhaus et al [16], while the effect of polymer molecular weight on filament thinning was studied by Arratia et al [15,18]. In a recent paper, Derzsi et al [13] presented an experimental study of the effects of viscoelasticity in microfluidic flow-focusing geometries. The authors find that the viscoelasticity of the focusing liquid stabilizes the jets facilitating formation of smaller droplets, and leads to transitions between various regimes at lower ratios of flow and at lower values of the Capillary numbers in comparison to the Newtonian focusing liquids.…”

Section: Introductionmentioning

confidence: 99%

“…Common droplet generator designs used in these devices are T-shaped [9,10] and flow-focusing [11,12,13] geometries. In T-shaped geometries, a dispersed (d) phase is injected perpendicularly into the main channel containing a continuous (c) phase.…”

Section: Introductionmentioning

confidence: 99%

Effects of viscoelasticity on droplet dynamics and break-up in microfluidic T-Junctions: a lattice Boltzmann study

Gupta

Sbragaglia

2016

Eur. Phys. J. E

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Abstract. The effects of viscoelasticity on the dynamics and break-up of fluid threads in microfluidic T-junctions are investigated using numerical simulations of dilute polymer solutions at changing the Capillary number (Ca), i.e. at changing the balance between the viscous forces and the surface tension at the interface, up to Ca ≈ 3 × 10 −2 . A NavierStokes (NS) description of the solvent based on the lattice Boltzmann models (LBM) is here coupled to constitutive equations for finite extensible non-linear elastic dumbbells with the closure proposed by Peterlin (FENE-P model). We present the results of three-dimensional simulations in a range of Ca which is broad enough to characterize all the three characteristic mechanisms of breakup in the confined T-junction, i.e. squeezing, dripping and jetting regimes. The various model parameters of the FENE-P constitutive equations, including the polymer relaxation time τ P and the finite extensibility parameter L 2 , are changed to provide quantitative details on how the dynamics and break-up properties are affected by viscoelasticity. We will analyze cases with Droplet Viscoelasticity (DV), where viscoelastic properties are confined in the dispersed (d) phase, as well as cases with Matrix Viscoelasticity (MV), where viscoelastic properties are confined in the continuous (c) phase. Moderate flow-rate ratios Q ≈ O(1) of the two phases are considered in the present study. Overall, we find that the effects are more pronounced in the case with MV, as the flow driving the break-up process upstream of the emerging thread can be sensibly perturbed by the polymer stresses.

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“…Typically, it is observed that elasticity of the droplet liquid prolongs the processes of thinning of the filament and significantly increases the interval required for breakup to complete. In a recent paper Garstecki et al [9] presented an experimental comparative study of the effect of elasticity of the continuous liquid in generation of droplets in microfluidic flow-focusing devices. The authors find that the elasticity of the focusing liquid stabilizes the jets facilitating formation of smaller droplets, and leads to transitions between various regimes at lower ratios of flow and at lower values of the Capillary numbers in comparison to the Newtonian focusing liquids.…”

Section: Introductionmentioning

confidence: 99%

“…In particular, droplet-based microfluidic devices have gained a considerable deal of attention due to their importance in studies that require high throughput control over droplet size [2,3,4,5]. Common droplet generator designs used in these devices are T-shaped geometries [6] and flow-focusing devices [7,8,9]. In T-shaped geometries, a dispersed (d) phase is injected perpendicularly into the main channel containing a continuous (c) phase.…”

Section: Introductionmentioning

confidence: 99%

Viscoelastic multicomponent fluids in confined flow-focusing devices

Gupta

Sbragaglia

Foard

et al. 2015

AIP Conference Proceedings

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Abstract. The effects of elasticity on the break-up of liquid threads in microfluidic cross-junctions is investigated using numerical simulations based on the "lattice Boltzmann models" (LBM). Working at small Capillary numbers, we investigate the effects of non-Newtonian phases in the transition from droplet formation at the cross-junction (DCJ) and droplet formation downstream of the cross-junction (DC) (Liu & Zhang, Phys. Fluids. 23, 082101 (2011)). Viscoelasticity is found to influence the break-up point of the threads, which moves closer to the cross-junction and stabilizes. This is attributed to an increase of the polymer feedback stress forming in the corner flows, where the side channels of the device meet the main channel.

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Flow focusing with viscoelastic liquids

Cited by 58 publications

References 58 publications

Generation of Oil Droplets in a Non-Newtonian Liquid Using a Microfluidic T-Junction

Generation of Oil Droplets in a Non-Newtonian Liquid Using a Microfluidic T-Junction

Effects of viscoelasticity on droplet dynamics and break-up in microfluidic T-Junctions: a lattice Boltzmann study

Viscoelastic multicomponent fluids in confined flow-focusing devices

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