Microfluidic Dynamic Interfacial Tensiometry (μDIT)

Brosseau, Quentin; Vrignon, Jérémy; Baret, Jean‐Christophe

doi:10.1039/c3sm52543k

Cited by 121 publications

(132 citation statements)

References 52 publications

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“…These values lead to the determination of k ads = (1.4 ± 1) × 10 3 s −1 m 6 mol −2 . We note that the value of Γ ∞ corresponds to a value obtained for small head groups, compatible with our molecule and other data from the literature for fluorinated surfactants (32). It should be noted that we used our model for consistency.…”

Section: Resultssupporting

confidence: 67%

Surfactant adsorption kinetics in microfluidics

Riechers

Maes

Akoury

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Emulsions are metastable dispersions. Their lifetimes are directly related to the dynamics of surfactants. We design a microfluidic method to measure the kinetics of adsorption of surfactants to the droplet interface, a key process involved in foaming, emulsification, and droplet coarsening. The method is based on the pH decay in the droplet as a direct measurement of the adsorption of a carboxylic acid surfactant to the interface. From the kinetic measurement of the bulk equilibration of the pH, we fully determine the adsorption process of the surfactant. The small droplet size and the convection during the droplet flow ensure that the transport of surfactant through the bulk is not limiting the kinetics of adsorption. To validate our measurements, we show that the adsorption process determines the timescale required to stabilize droplets against coalescence, and we show that the interface should be covered at more than 90% to prevent coalescence. We therefore quantitatively link the process of adsorption/desorption, the stabilization of emulsions, and the kinetics of solute partitioning-here through ion exchange-unraveling the timescales governing these processes. Our method can be further generalized to other surfactants, including nonionic surfactants, by making use of fluorophore-surfactant interactions.droplet | interfaces | surfactant | emulsion | microfluidics S urface active compounds are ubiquitous in our daily life, be it in living systems or in industrial and technological products (1-3). The compounds are used widely for the stabilization of foams and emulsions for food and cosmetic products, painting materials, and industrial coatings (3). Emulsions are nowadays also used in combination with microfluidic systems for applications in biotechnology (3-11). An emulsion is a dispersion of one liquid phase into another, stabilized by surfactants in a metastable state. The kinetic stabilization of emulsions occurs through several mechanisms, involving electrostatic or steric repulsion and the buildup of Marangoni stresses to improve the lifetime of emulsions against coalescence (12, 13). On the other hand, surfactants are involved in transport processes such as Ostwald ripening or solute transport, which mediates the chemical equilibration of the system (14-17): in general, all processes affecting the lifetime of emulsions (coalescence, rupture, exchange, and loss of molecules) are directly related to the physics and dynamics of the surfactant molecules at interfaces (3,4,6,10,11,15,16). The first analysis of surfactant layers dates back to the 18th century with Franklin's experiments (1) and the first comprehensive studies on adsorption kinetics by Ward and Tordai (18) and Langmuir (19). From this point, a wide variety of models describe the adsorption dynamics, accounting for all kinds of molecular effects at interfaces (20-26). We expect two limiting cases: (i) the adsorption is limited by the bulk transport toward the interface, leading to a local equilibrium between the surfactant interfacial concen...

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Section: Resultssupporting

confidence: 67%

Surfactant adsorption kinetics in microfluidics

Riechers

Maes

Akoury

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

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“…The time-invariant values seen for different bulk NA concentrations (CNA) are due to the changes in the composition of the n-heptane phase, reducing slightly from the value for the n-heptane/water interface. The results also indicate that adsorption is rapid compared with the experimental timescale, being complete in <0.3 s. Using a microfluidic technique, adsorption at the hydrocarbon/water interface has recently been shown [55] to occur on the millisecond timescale, more rapidly than previously thought. (8)).…”

Section: Na Adsorption At the N-heptane/water Interfacementioning

confidence: 54%

Metal Ion Interactions with Crude Oil Components: Specificity of Ca2+ Binding to Naphthenic Acid at an Oil/Water Interface

Taylor

Chu

2018

Colloids and Interfaces

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Abstract:On the basis of dynamic interfacial tension measurements, Ca 2+ has been shown specifically to interact with naphthenic acid (NA) at the n-heptane/water interface, consistent with NA adsorption followed by interfacial complexation and formation of a more ordered interfacial film. Optimum concentrations of Ca 2+ and NA have been found to yield lower, time-dependent interfacial tensions, not evident for Mg 2+ and Sr 2+ or for several alkali metal ions studied. The results reflect the specific hydration and coordination chemistry of Ca 2+ seen in biology. Owing to the ubiquitous presence of Ca 2+ in oilfield waters, this finding has potential relevance to the surface chemistry underlying crude oil recovery. For example, "locking" acidic components at water/oil interfaces may be important for crude oil emulsion stability, or in bonding bulk oil to mineral surfaces through an aqueous phase, potentially relevant for carbonate reservoirs. The relevance of the present results to low salinity waterflooding as an enhanced crude oil recovery technique is also discussed.

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“…The ratio of K d to K w for the surfactant was set at 1000 to mimic the known preference for EA surfactant to stabilise droplets. 38 This model is applicable to any system where K d is larger that K w . A second surfactant was also introduced into the model at 10% abundance compared to the first surfactant, with a distribution coefficient ratio of 0.01.…”

Section: Resultsmentioning

confidence: 99%

Droplet confinement and leakage: Causes, underlying effects, and amelioration strategies

2015

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The applicability of droplet-based microfluidic systems to many research fields stems from the fact that droplets are generally considered individual and selfcontained reaction vessels. This study demonstrates that, more often than not, the integrity of droplets is not complete, and depends on a range of factors including surfactant type and concentration, the micro-channel surface, droplet storage conditions, and the flow rates used to form and process droplets. Herein, a model microfluidic device is used for droplet generation and storage to allow the comparative study of forty-four different oil/surfactant conditions. Assessment of droplet stability under these conditions suggests a diversity of different droplet failure modes. These failure modes have been classified into families depending on the underlying effect, with both numerical and qualitative models being used to describe the causative effect and to provide practical solutions for droplet failure amelioration in microfluidic systems. V C 2015 AIP Publishing LLC.

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Microfluidic Dynamic Interfacial Tensiometry (μDIT)

Cited by 121 publications

References 52 publications

Surfactant adsorption kinetics in microfluidics

Surfactant adsorption kinetics in microfluidics

Metal Ion Interactions with Crude Oil Components: Specificity of Ca2+ Binding to Naphthenic Acid at an Oil/Water Interface

Droplet confinement and leakage: Causes, underlying effects, and amelioration strategies

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