Micron-sized double emulsions and nematic shells generated via tip streaming

He, Kunyun; Campo-Cortés, F.; Goral, Martyna; López-León, Teresa; Gordillo, José Manuel

doi:10.1103/physrevfluids.4.124201

Cited by 10 publications

(10 citation statements)

References 29 publications

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“…In this geometry, the dispersed phase is in-Figure 47: Shells produced with the confined selective withdrawal geometry for different speeds in the extraction tube. The shell diameter decreases as the speed decreases [447].…”

Section: Selective Withdrawal and Electrified Filmsmentioning

confidence: 97%

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Dripping, jetting and tip streaming

2020

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Dripping, jetting and tip streaming have been studied up to a certain point separately by both fluid mechanics and microfluidics communities, the former focusing on fundamental aspects while the latter on applications. Here, we intend to review this field from a global perspective by considering and linking the two sides of the problem. In the first part, we present the theoretical model used to study interfacial flows arising in droplet-based microfluidics, paying attention to three elements commonly present in applications: viscoelasticity, electric fields and surfactants. We review both classical and current results about the stability of jets affected by these elements. Mechanisms leading to the breakup of jets to produce drops are reviewed as well, including some recent advances in this field. We also consider the relatively scarce theoretical studies on the emergence and stability of tip streaming in open systems. In the second part of this review, we focus on axisymmetric microfluidic configurations which can operate on the dripping and jetting modes either in a direct (standard) way or via tip streaming. We present the dimensionless parameters characterizing these configurations, the scaling laws which allow predicting the size of the resulting droplets and bubbles, as well as those delimiting the parameter windows where tip streaming can be found. Special attention is paid to electrospray and flow focusing, two of the techniques more frequently used in continuous drop production microfluidics. We aim to connect experimental observations described in this section of topics with fundamental and general aspects described in the first part of the review. This work closes with some prospects at both fundamental and practical levels.

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Section: Selective Withdrawal and Electrified Filmsmentioning

confidence: 97%

“…It can also be used to coat microparticles present in the withdrawn liquid [29]. A confined selective withdrawal geometry has been used to produce bubbles [446], emulsions [176], double emulsions and nematic shells [447] (Fig. 47), and micro-sized PDMS particles [351] in the tip streaming regime.…”

Section: Selective Withdrawal and Electrified Filmsmentioning

confidence: 99%

Dripping, jetting and tip streaming

2020

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“…2001) and confined selective withdrawal (He et al. 2019) configurations, where the focusing phenomenon is caused by a cylindrical capillary located in front of a liquid film and meniscus, respectively.…”

Section: Introductionmentioning

confidence: 99%

“…Liquid-liquid SJTS can also be produced in configurations similar to flow focusing, such as the coflowing configuration (Suryo & Basaran 2006;Marín, Campo-Cortés & Gordillo 2009;Rubio-Rubio, Sevilla & Gordillo 2013), where the effect produced by the discharge orifice is not present, or the selective withdrawal (Cohen et al 2001) and confined selective withdrawal (He et al 2019) configurations, where the focusing phenomenon is caused by a cylindrical capillary located in front of a liquid film and meniscus, respectively.…”

Section: Introductionmentioning

confidence: 99%

Global stability analysis of axisymmetric liquid–liquid flow focusing

et al. 2020

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“…Flow focusing (Gañán-Calvo & Riesco-Chueca 2006) and confined selective withdrawal (Evangelio, Campo-Cortés & Gordillo 2015;Evangelio et al 2016;Muñoz-Sánchez et al 2016;He et al 2019) are similar techniques to produce several microfluidic entities based on the hydrodynamic focusing principle. As shown in figure 1, the only difference between them is the shape of the discharge orifice located in front of the feeding capillary.…”

Section: Introductionmentioning

confidence: 99%

On the hydrodynamic focusing for producing microemulsions via tip streaming

et al. 2022

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In this work we study experimentally and numerically the stability of hydrodynamic focusing to produce microemulsions. The jetting regime was produced experimentally for the lowest outer viscosity, while microdripping was obtained for the highest outer viscosity. The liquid ejection for small capillary numbers stabilizes as the distance between the feeding capillary and the focusing orifice decreases. The comparison between confined selective withdrawal and stretched flow focusing for the largest outer viscosity shows that confined selective withdrawal significantly enhances the stability of the microdripping mode, which entails a significant reduction of the minimum value of the droplet diameter. When surfactants are dissolved in the inner liquid at sufficiently large concentrations, we observe a significant decrease in both the minimum flow rate leading to tip streaming and the droplet diameter. The surfactant monolayer stabilizes the meniscus and promotes the transition from microdripping to jetting. The global stability analysis shows that jetting via tip streaming becomes unstable due to the growth of an oscillatory perturbation. The unstable perturbation affects the tapering meniscus for the lowest outer viscosity, which explains why the meniscus oscillates in the experiments. The critical flow rate ratio is accurately predicted by the global stability analysis in most of the experiments with the lowest outer viscosity. For the highest outer viscosity, the global stability analysis correctly predicts the microdripping mode and allows one to calculate the droplet emission frequency in that mode.

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Micron-sized double emulsions and nematic shells generated via tip streaming

Cited by 10 publications

References 29 publications

Dripping, jetting and tip streaming

Dripping, jetting and tip streaming

Global stability analysis of axisymmetric liquid–liquid flow focusing

On the hydrodynamic focusing for producing microemulsions via tip streaming

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