Competition Between Viscoelasticity and Surfactant Dynamics in Flow Focusing Microfluidics

Lee, Wingki; Walker, Lynn M.; Anna, Shelley L.

doi:10.1002/mame.201000302

Cited by 50 publications

(32 citation statements)

References 48 publications

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“…These stresses retard the drainage of the inner fluid from the thread, thus prolonging the necking stage in comparison to when surfactants are absent. Similar observations have been reported in microfluidic flow focusing devices during necking in the presence of surfactants [51][52][53].…”

Section: Modification To the Droplet Formation Modelsupporting

confidence: 87%

Droplet formation in microfluidic T-junction generators operating in the transitional regime. III. Dynamic surfactant effects

Glawdel

Ren

2012

Phys. Rev. E

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This study extends our previous work on droplet generation in microfluidic T-junction generators to include dynamic interfacial tension effects created by the presence of surfactants. In Paper I [T. Glawdel, C. Elbuken, and C. L. Ren, Phys. Rev. E 85, 016322 (2012)], we presented experimental findings regarding the formation process in the squeezing-to-transition regime, and in Paper II [T. Glawdel, C. Elbuken, and C. L. Ren, Phys. Rev. E 85, 016323 (2012)] we developed a theoretical model that describes the performance of T-junction generators without surfactants. Here we study dynamic interfacial tension effects for two surfactants, one with a small molecular weight that adsorbs quickly, and the other with a large molecular weight that adsorbs slowly. Using the force balance developed in Paper II we extract the dynamic interfacial tension from high speed videos obtained during experiments. We then develop a theoretical model to predict the dynamic interfacial tension in microfluidic T-junction generators as a function of the surfactant properties, flow conditions, and generator design. This model is then incorporated into the overall model for generator performance to effectively predict the size of droplets produced when surfactants are present.

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Section: Modification To the Droplet Formation Modelsupporting

confidence: 87%

Droplet formation in microfluidic T-junction generators operating in the transitional regime. III. Dynamic surfactant effects

Glawdel

Ren

2012

Phys. Rev. E

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“…Such effects have been observed often in the past in systems in interfacial phenomena involving surfactant below the saturated concentration. Analogous effects have been found by the group Anna 5,60 or by Fernandez and Homsy 61 in similar configurations. The origin can be found in the complex surfactant dynamics at the moving interface with low electrical shear actuating at the interface, which is only partially covered by surfactant.…”

Section: Intermediate Regimessupporting

confidence: 82%

Surface tension effects on submerged electrosprays

2012

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Electrosprays are a powerful technique to generate charged micro/nanodroplets. In the last century, the technique has been extensively studied, developed, and recognized with a shared Nobel price in Chemistry in 2002 for its wide spread application in mass spectrometry. However, nowadays techniques based on microfluidic devices are competing to be the next generation in atomization techniques. Therefore, an interesting development would be to integrate the electrospray technique into a microfluidic liquid-liquid device. Several works in the literature have attempted to build a microfluidic electrospray with disputable results. The main problem for its integration is the lack of knowledge of the working parameters of the liquid-liquid electrospray. The "submerged electrosprays" share similar properties as their counterparts in air. However, in the microfluidic generation of micro/nanodroplets, the liquid-liquid interfaces are normally stabilized with surface active agents, which might have critical effects on the electrospray behavior. In this work, we review the main properties of the submerged electrosprays in liquid baths with no surfactant, and we methodically study the behavior of the system for increasing surfactant concentrations. The different regimes found are then analyzed and compared with both classical and more recent experimental, theoretical and numerical studies. A very rich phenomenology is found when the surface tension is allowed to vary in the system. More concretely, the lower states of electrification achieved with the reduced surface tension regimes might be of interest in biological or biomedical applications in which excessive electrification can be hazardous for the encapsulated entities.

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“…(13) and (15) and the number ratio n f actually reflects the ratio of bubble and droplet generation frequencies, n f equals to f W */f G +1. (13) and (15) and the number ratio n f actually reflects the ratio of bubble and droplet generation frequencies, n f equals to f W */f G +1.…”

Section: Size Laws Of Generated Bubbles and Dropletsmentioning

confidence: 99%

Generating Gas‐Liquid‐Liquid Three‐Phase Microflows in a Cross‐Junction Microchannel Device

Wang

Kang

et al. 2013

Chem Eng & Technol

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The generation of gas‐liquid‐liquid three‐phase microflows in a cross‐junction microchannel device is experimentally analyzed. Three gas‐phase and eight water‐phase flow manners at the cross junction are described with oil phase as continuous phase. Comparing with the gas‐liquid and liquid‐liquid two‐phase microflows, similar flow behaviors of dispersed phases exist in the three‐phase processes but new capillary numbers as well as the phase ratio of dispersed phases need to be introduced in the flow maps to distinguish the complicated three‐phase flow modes. Although the three‐phase flows are mercurial at the channel junction, only six flow patterns are observed in the downstream microchannel. According to the experimental results, the effects of bubble/droplet generation manners on their size distributions are indicated. The generation mechanisms of bubbles and droplets are analyzed and correlated equations are established for their average volumes.

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Competition Between Viscoelasticity and Surfactant Dynamics in Flow Focusing Microfluidics

Cited by 50 publications

References 48 publications

Droplet formation in microfluidic T-junction generators operating in the transitional regime. III. Dynamic surfactant effects

Droplet formation in microfluidic T-junction generators operating in the transitional regime. III. Dynamic surfactant effects

Surface tension effects on submerged electrosprays

Generating Gas‐Liquid‐Liquid Three‐Phase Microflows in a Cross‐Junction Microchannel Device

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