Numerical Study of Surfactant Dynamics during Emulsification in a T-Junction Microchannel

Riaud, Antoine; Zhang, Hao; Wang, Xueying; Wang, Kai; Luo, Guangsheng

doi:10.1021/acs.langmuir.8b00123

Cited by 35 publications

(31 citation statements)

References 80 publications

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“…The surface density of the surfactant is higher at the two poles of the droplet than at the flat parts adjacent to the channel walls. It is a little higher at the front pole of the droplet as compared to that at the rear which is in confirmation with the results of Riaud et al [32]. The variation of the surfactant concentration at the front pole of the droplet is shown in Fig.…”

Section: Effect Of Surfactant On Droplet Generationsupporting

confidence: 90%

“…Numerical simulations can help identify the influence of surfactant concentration at the droplet/ bubble interface [31]. The influence of surfactant (Span 80 mixed with octane) on droplet generation was numerically investigated using Lattice Boltzmann Method [32]. This study uses two computational models to present uniform and non-uniform distribution of surfactant at the interface.…”

Section: Introductionmentioning

confidence: 99%

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Simulation studies on picolitre volume droplets generation and trapping in T-junction microchannels

2020

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In this paper, we present simulation studies on the formation of water microdroplets in mineral oil in a T-junction Microfluidics device. We have studied the droplet generation in two different regimes, viz., squeezing and squeezing to dripping transition regime. The effect of fluid flow rates, and surfactant concentration on the droplet generation has been investigated. It is seen that a rise in the concentration of surfactant by 4%, increases the frequency of droplet generation by 16% at the higher capillary number (C a = 0.02), whereas, there is only a marginal or no change in the case of squeezing regime (C a = 0.0028-0.008). We have also studied the trapping of the generated microdroplets in microwells. It is observed that the trapping of the droplet is highly influenced by the viscous drag force, droplet length, the surface energy of the droplet, droplet speed, depth of the Well for trapping and alignment of the two plates constituting the device. Our studies reveal that the droplets travelling faster than a critical trapping velocity do not get trapped in the Well. Addition of a surfactant to the mineral oil is seen to lead to a significant reduction in the critical velocity for the droplet trapping. Trapping of droplets travelling at velocities close to the critical velocity for trapping depends strongly on the alignment of the two plats of the Slip-Chip device.

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Section: Effect Of Surfactant On Droplet Generationsupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Simulation studies on picolitre volume droplets generation and trapping in T-junction microchannels

2020

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“…In industrial processes or natural situations, surface bubbles drain within contaminated liquids. In those situations, the drainage rate is considerably decreased due to Marangoni stresses induced by surface tension gradients along the bubble interface and associated surface viscous shear due to the immobilization of the interfaces [14], [15], [16], [17]. In this situation and in the limit of immobile interfaces and large bubbles (Bo 1), the competition between gravitational drainage and viscous shear stresses gives rise to an algebraic decay of the film thickness of the form [18,19]…”

Section: Introductionmentioning

confidence: 99%

Lifetime of Surface Bubbles in Surfactant Solutions

et al. 2020

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Despite the prevalence of surface bubbles in many natural phenomena and engineering applications, the effect of surfactants on their surface residence time is not clear. Numerous experimental studies and theoretical models exist but a clear understanding of the film drainage phenomena is still lacking. In particular, theoretical works predicting the drainage rate of the thin film between a bubble and the free surface in the presence and absence of surfactants usually make use of the lubrication theory. On the other hand, in numerous natural situation and experimental works, the bubble approaches the free surface from a certain distance and forms a thin film at a later stage. This paper attempts to bridge these two approaches. In particular, in this paper, we review these works, and compare them to our Direct Numerical Simulations where we study the coupled influence of bubble deformation and surfactants on the rising and drainage process of a bubble beneath a free surface. In the present study, the level-set method is used to capture the air-liquid interfaces and the transport equation of surfactants is solved in an Eulerian framework. The axisymmetric simulations capture the bubble acceleration, deformation and rest (or drainage) phases from non-deformable to deformable bubbles, as measured by the Bond number (Bo), and from surfactant-free to surfactant coated bubbles, as measured by the Langmuir number (La). The results show that the distance h between the bubble and the free surface decays exponentially for surfactant-free interfaces (La = 0) and this decay is faster for non-deformable bubbles (Bo 1) than for deformable ones (Bo 1). The presence of surfactants (La > 0) slows down the decay of h, exponentially for large bubbles (Bo 1) and algebraically for small ones (Bo 1). For Bo ∼ 1, the lifetime is the longest and associated to (Marangoni) elasticity of the interfaces.

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“…for both oil-ferrofluid and oil-mixture interfacial tensions. 40,49,50 Given that the two miscible fluids have very close properties, it would be a valid assumption to ignore the Marangoni effect in the solution as frequently being assumed in previous works on mixing inside droplets. 28,42 The The effective dimensionless numbers in this study are Reynolds, Peclet and Capillary numbers.…”

Section: Magnetic Field Effect On Bulk Flow Mixing Improvementmentioning

confidence: 99%

Effects of magnetic nanoparticles on mixing in droplet-based microfluidics

et al. 2019

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High-throughput, rapid and homogeneous mixing of microdroplets in a small length scale such as that in a microchannel is of great importance for lab-on-a-chip applications. Various techniques for mixing enhancement in microfluidics have been extensively reported in the literature. One of these techniques is the mixing enhancement with magnetofluidics using ferrofluid, a liquid with dispersed magnetic nanoparticles. However, a systematic study exploring the mixing process of ferrofluid and its influencing parameters is lacking. The present study numerically examines the effect of key parameters including magnetic field,

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Numerical Study of Surfactant Dynamics during Emulsification in a T-Junction Microchannel

Cited by 35 publications

References 80 publications

Simulation studies on picolitre volume droplets generation and trapping in T-junction microchannels

Simulation studies on picolitre volume droplets generation and trapping in T-junction microchannels

Lifetime of Surface Bubbles in Surfactant Solutions

Effects of magnetic nanoparticles on mixing in droplet-based microfluidics

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