Studying coalescence at different lengthscales: from films to droplets

Chatzigiannakis, Emmanouil; Chen, Yun; Bachnak, Rana; Dutcher, Cari S.; Vermant, Jan

doi:10.1007/s00397-022-01365-w

Cited by 12 publications

(9 citation statements)

References 102 publications

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“…The results are consistent with the findings of Narayan et al 18,19 for water and mineral oil systems. There is also a good agreement between these microfluidic measurements and dynamic thin-film balance methods shown by Chatzigiannakis et al, 43 suggesting that the observations presented here are valid across both film-and droplet-based methodologies for studying coalescence.…”

Section: Resultsmentioning

confidence: 99%

The Effect of Surface Interactions on the Coalescence of Water Droplets in Fuel

Bachnak,

Panigrahi,

Moravec

et al. 2023

Energy Fuels

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Coalescence is a heavily utilized treatment for phase separation of emulsions, especially in the industrial application of filtration. In fuel filtration, the water must be filtered out to prevent the corrosion of engine parts due to microbial growth. The coalescing filters used often contain fibers, to which the droplets first adhere before coalescing with incoming droplets to form larger drops. The contact with both fibers and other droplets certainly affects the coalescence process, but the extent of the impact remains relatively undercharacterized. In this work, the effect of surface interactions on droplet coalescence is studied by using microfluidic platforms. The film drainage times for water droplets suspended in fuel are measured in a contact device that studies the coalescence of droplets in contact with poly(dimethylsiloxane) (PDMS) traps and are compared to those found using a contactless microfluidic Stokes trap device that studies the coalescence of free droplets in a hydrodynamic cross-slot. The fuel contains mono-olein, a common molecule in biodiesel that acts as a surface-active surfactant at a fuel–water interface. A dimensionless film drainage time is compared at different capillary numbers (Ca), for the contact and contactless cases. It is found that for both cases the dimensionless drainage time is decreasing as a function of Ca. In addition, the coalescence events for droplets with multiple contacts, either with other droplets or with the PDMS droplet traps, had a lower dimensionless drainage time than that between two free droplets brought together in the Stokes trap. This work aims to serve as a foundation to understand coalescence for essential industrial applications such as firefighting foams, oil remediation, or pharmaceutical preparation.

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Section: Resultsmentioning

confidence: 99%

The Effect of Surface Interactions on the Coalescence of Water Droplets in Fuel

Bachnak,

Panigrahi,

Moravec

et al. 2023

Energy Fuels

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“…This includes comparison between bottle tests and drops collision 11 as well as comparisons between thin films and microfluidic methods. 14 Centrifugation and FFT methods lead respectively to a critical osmotic pressure and to a critical capillary pressure for the onset of coalescence. Experiments performed with a protein as an emulsifier did not allow for a quantitative comparison due to the different procedures for preparation of samples, likely resulting in different drop surface coverages.…”

Section: Introductionmentioning

confidence: 99%

Comparison of Methods Used to Investigate Coalescence in Emulsions

Plassard,

Mouret,

Nieto-Draghi

et al. 2024

Langmuir

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We present a study of moderately stable dilute emulsions. These emulsions are models for water contaminated by traces of oil encountered in many water treatment situations. The purification of water and the elimination of oil rely on the emulsion stability. Despite actively being studied, the topic of emulsion stability is still far from being fully understood. In particular, it is still unclear whether experimental methods accessing different length scales lead to the same conclusions. In the study presented in this paper, we have used different methods to characterize the emulsions, such as centrifugation and simple bottle tests, as well as investigations of the collision of single macroscopic oil drops at an oil–water interface. We studied different emulsions containing added polymer or surfactant. In the case of added polymer, centrifugation and single drop experiments led to opposite trends in stability when the polymer concentration is varied. In the case of added surfactant, both centrifugation and single drop experiments show a maximum stability when the surfactant concentration is increased, whereas bottle tests show a monotonous increase in stability. We propose tentative interpretations of these unexpected observations. The apparent contradictions are due to the fact that different methods require different drop sizes or different drop concentrations. The puzzling decrease in emulsion stability at a higher surfactant concentration observed with some methods, however, remains unclear. This coalescence study illustrates the fact that different results can be obtained when different experimental methods are used. It is therefore advisable not to rely on a single method, especially in the case of emulsions of limited stability for reasons explained in the paper.

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“…In this geometry, the aqueous thin film possesses two opposing lipid monolayers that are brought together during drainage, analogous to the first stage of fusion where opposing lipid leaflets come together. Thin film setups are typically used to study the interactions between capillarity and hydrodynamics in retraction, the effect of ionic strength on film stabilization, , kinetics of domain expansion, , and coalescence . In this study, we focus on the effect of increasing NaCl and CaCl 2 concentrations on lipid monolayer interactions.…”

Section: Introductionmentioning

confidence: 99%

“…Thin film setups are typically used to study the interactions between capillarity and hydrodynamics in retraction, 26 the effect of ionic strength on film stabilization, 27,28 kinetics of domain expansion, 29,30 and coalescence. 31 In this study, we focus on the effect of increasing NaCl and CaCl 2 concentrations on lipid monolayer interactions. Dioleoyl chains with varied headgroup composition are chosen due to their biological presence, good working temperature range, and existing literature data.…”

Section: ■ Introductionmentioning

confidence: 99%

Effects of Ion Concentration and Headgroup Chemistry on Thin Lipid Film Drainage

Zabala-Ferrera,

Beltramo

2023

Langmuir

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While the use of lipid nanoparticles in drug delivery applications has grown over the past few decades, much work remains to be done toward the characterization and rational design of the drug carriers. A key feature of delivery is the interaction of the exterior leaflet of the LNP with the outer leaflet of the cell membrane, which relies in part on the fusogenicity of the lipids and the ionic environment. In this paper, we study the interactions between two lipid monolayers using a thin film balance to create lipid thin films and interferometry to measure film evolution. We probe the role of lipid headgroup chemistry and charge, along with ionic solution conditions, in either promoting or hindering film drainage and stability. Specific headgroups phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylglycerol (PG), and phosphatidylserine (PS) are chosen to represent a combination of charge and fusogenicity. We quantify each film's drainage characteristics over a range of capillary numbers. Qualitatively, we find that films transition from drainage via a large dimple to drainage via channels and vortices as the capillary number increases. Additionally, we observe a transition from electrostatically dominated film drainage at low CaCl 2 concentrations to fusogenic-dominated film drainage at higher CaCl 2 concentrations for anionic fusogenic (PS) films. Understanding the role of headgroup composition, ionic composition, and ionic concentration will pave the way for the design of tunable vesicle and buffer systems that behave desirably across a range of ex vivo and in vivo environments.

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Studying coalescence at different lengthscales: from films to droplets

Cited by 12 publications

References 102 publications

The Effect of Surface Interactions on the Coalescence of Water Droplets in Fuel

The Effect of Surface Interactions on the Coalescence of Water Droplets in Fuel

Comparison of Methods Used to Investigate Coalescence in Emulsions

Effects of Ion Concentration and Headgroup Chemistry on Thin Lipid Film Drainage

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