Adsorption of nonionic surfactants at fluid–fluid interfaces: Importance in the coalescence of bubbles and drops

Giribabu, K.; Ghosh, Pallab

doi:10.1016/j.ces.2007.03.002

Cited by 71 publications

(75 citation statements)

References 31 publications

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“…As such, for moderate surfactant concentrations, the surfactant monolayers in the system are populated according to Langmuir isotherm kinetics. 35 The ubiquity of surfactants within droplet microfluidic systems and the enormous effect they have on droplet behaviour means that almost any aberrant droplet behaviours must be considered in terms of surfactant distribution rather than solely in terms of physical characteristics such as shear flow.…”

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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Section: Resultsmentioning

confidence: 99%

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

2015

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“…This behaviour is a result of the surface tension force inability to overcome the electrostatic force, as for the same size drop pair in the absence of surfactants a complete coalescence is observed. In the absence of an electric field, the non-polar tail of SDS surfactant covers the drops surfaces, especially in the area of approaching drop faces and prevents the two drops from direct contact which is necessary for coalescence [48]. In the presence of an electric field, as soon as an electrical contact is established the two drops experience charge transfer and polarisation, subjecting the drops to a pull off force, breaking the formed bridge after a very short time leading to a non-coalescence pattern.…”

Section: Drop-drop Coalescencementioning

confidence: 99%

Electro-coalescence of water drops in oils under pulsatile electric fields

Mousavi

Ghadiri

Buckley

2014

Chemical Engineering Science

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For the separation of disperesed water drops from oils an electric field may be used to enhance their coalescence. However, this process could cause some undesirable phenomena such as secondary droplets formation, reducing the separation efficiency. Here the effect of pulsatile electric fields (PEF) on the secondary droplets formation has been investigated. In the presence of a very low frequency PEF or DC electric field three distinct drop-drop and drop-interface interaction patterns are observed: complete coalescence, partial coalescence and rebound without coalescence. The first is the ideal pattern not leaving any secondary droplets. It has previously been shown that an increase in the electric field strength and/or a decrease in the interfacial tension result in non-ideal patterns in dropinterface coalescence. The application of PEF shifts the coalscence pattern from a non-ideal to an ideal one in both drop-drop and drop-interface coalescences. Three waveform types, i.e. square, sinusoidal and sawtooth waves have been applied to the coalescence process. It is shown that the sawtooth waveform is the most effective in reducing the secondary droplets formation in dropinterface coalescence, followed closely by the sinusoidal one. The observation of videos sequences suggests that a threshold frequency exists above which a non-ideal pattern switches to an ideal one. For drop-drop coalescence this threshold frequency depends on the PEF amplitude and the size of primary drop pairs, as for bigger primary drop pairs and larger amplitudes of PEF the threshold frequency would be higher. When using pulsatile electric fields higher field strengths can be applied for systems having a high water content without causing field breakdown, as compared to constant DC field. This is useful in optimizing the electro-coalescence process.

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“…The cmc of TX100 in water is about 210 -4 M [25], and thus TX100 micelles did not form in the present study. The  sat and K values for TX100 at the toluene/water interface have already been reported [25] and are listed in Table 2.…”

Section: In-plane Fluorescence Anisotropy At the Tx100-modified Toluementioning

confidence: 86%

“…The  sat and K values for TX100 at the toluene/water interface have already been reported [25] and are listed in Table 2. From these, the  values were calculated to be 9.610 -7 , 1.110 -6 , and…”

Section: In-plane Fluorescence Anisotropy At the Tx100-modified Toluementioning

confidence: 99%

See 1 more Smart Citation

Microscopic Imaging of Fluorescence Anisotropy of Rhodamine B at the Free and Surfactant-Modified Toluene/Water Interfaces Excited under Total Internal Reflection Conditions

Tsukahara

Yamasaki

Fujiwara

2010

SERDJ

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The present study successfully carried out microscopic imaging of the steady-state in-plane fluorescence anisotropy ( in r ) of rhodamine B at the free and surfactant-modified toluene/water interfaces excited under total internal reflection conditions with an inverted microscope, a laser system, a linear polarizer, and a CCD camera, which were easy to operate and inexpensive. As surfactants, sodium dodecylsulfate (SDS), Triton X-100 (TX100), and dihexadecyl hydrogen phosphate (Hdhp) were used. The microscopic in r images were almost homogeneous regardless of the types and concentrations of surfactants, implying homogeneous interfaces. On the other hand, the peaks of the fluorescence spectrum of interfacial rhodamine B and averaged in r values depended on the types and concentrations of the surfactants. This in r dependency was mainly attributable to the change of the rotational dynamics of interfacial rhodamine B by solvation. These results suggested that the proposed method would be a promising one to evaluate the homogeneity of liquid/liquid interfaces and the reactivity of solutes at the interface.

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Adsorption of nonionic surfactants at fluid–fluid interfaces: Importance in the coalescence of bubbles and drops

Cited by 71 publications

References 31 publications

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

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

Electro-coalescence of water drops in oils under pulsatile electric fields

Microscopic Imaging of Fluorescence Anisotropy of Rhodamine B at the Free and Surfactant-Modified Toluene/Water Interfaces Excited under Total Internal Reflection Conditions

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