Special Issue "Selected Papers from Bubble & Drop 2017"

A special issue of Colloids and Interfaces (ISSN 2504-5377).

Deadline for manuscript submissions: closed (30 December 2017)

Special Issue Editors

Guest Editor
Dr. Reinhard Miller

Max Planck Institute of Colloids and Interfaces, D-14424, Golm, Germany
Website | E-Mail
Interests: dynamics and mechanics of liquid interfaces; thermodynamics of adsorption of surfactants and proteins; interfacial interactions and 2D rheology; stability of foams and emulsions
Guest Editor
Dr. Alain Cagna

TECLIS Instruments, Tassin, 69160 Lyon Métropole, France
Website | E-Mail
Interests: engineering physics; interfaces and foam characterization; interfacial rheology; engineering instrumentation; optics

Special Issue Information

Dear Colleagues,

The Bubble and Drop workshop (http://www.bd2017-lyon.fr/) is a scientific event that gathers scientists from academia and industry, working in the world of various types of interfaces, emulsion, and foams. The conference provides a podium for presenting scientific posters and oral contributions, dealing with fundamental research and industrial applications, all dealing somehow with drops and bubbles. The meeting in 2017 is organized in Lyon and is the 7th in the series.

Participants of Bubble and Drop 2017 are cordially invited to contribute original research papers to this Special Issue of Colloids and Interfaces.

Dr. Reinhard Miller
Dr. Alain Cagna
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Colloids and Interfaces is an international peer-reviewed open access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) is waived for well-prepared manuscripts submitted to this issue. Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Bubble & drop formation, motion, interactions
  • Adsorption and interfacial dynamics
  • Interfacial rheology
  • Foams and emulsions
  • Liquid films between bubble & drop
  • Wetting and spreading
  • Bubble & drop in industrial applications

Published Papers (5 papers)

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Research

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Open AccessArticle Electroosmotic Flow in Free Liquid Films: Understanding Flow in Foam Plateau Borders
Colloids Interfaces 2018, 2(1), 8; https://doi.org/10.3390/colloids2010008
Received: 12 January 2018 / Revised: 25 February 2018 / Accepted: 26 February 2018 / Published: 28 February 2018
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Abstract
Liquid flow in foams mostly proceeds through Plateau borders where liquid content is the highest. A sufficiently thick (~180 µm) free liquid film is a reasonable model for understanding of electrokinetic phenomena in foam Plateau borders. For this purpose, a flow cell with
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Liquid flow in foams mostly proceeds through Plateau borders where liquid content is the highest. A sufficiently thick (~180 µm) free liquid film is a reasonable model for understanding of electrokinetic phenomena in foam Plateau borders. For this purpose, a flow cell with a suspended free liquid film has been designed for measurement of electrokinetic flow under an imposed electric potential difference. The free liquid film was stabilised by either anionic (sodium lauryl sulfate (NaDS)) or cationic (trimethyl(tetradecyl) ammonium bromide (TTAB)) surfactants. Fluid flow profiles in a stabilised free liquid film were measured by micron-resolution particle image velocimetry (µ-PIV) combined with a confocal laser scanning microscopy (CLSM) setup. Numerical simulations of electroosmotic flow in the same system were performed using the Finite Element Method. The computational geometry was generated by CLSM. A reasonably good agreement was found between the computed and experimentally measured velocity profiles. The features of the flow profiles and the velocity magnitude were mainly determined by the type of surfactant used. Irrespective of the surfactants used, electroosmotic flow dominated in the midfilm region, where the film is thinnest, while backflow due to pressure build-up developed near the glass rods, where the film is thickest. Full article
(This article belongs to the Special Issue Selected Papers from Bubble & Drop 2017)
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Open AccessArticle Composite Foaming Agents on the Basis of High-Molecular Natural Surfactants
Colloids Interfaces 2018, 2(1), 2; https://doi.org/10.3390/colloids2010002
Received: 2 December 2017 / Revised: 26 December 2017 / Accepted: 4 January 2018 / Published: 7 January 2018
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Abstract
Today, naturally occurring foam constituents and surface-active proteins with intriguing structures and functions are being identified from a variety of biological and chemical sources. In this paper we studied the colloid chemical properties of high-molecular natural surfactants such as keratin hydrolyzate (1.5–15%), gelatin
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Today, naturally occurring foam constituents and surface-active proteins with intriguing structures and functions are being identified from a variety of biological and chemical sources. In this paper we studied the colloid chemical properties of high-molecular natural surfactants such as keratin hydrolyzate (1.5–15%), gelatin (0.1–1%), and egg albumin (0.1–1%) in a wide concentration range. The foaming ability and foam-stabilizing properties of mixtures of these proteins were established. The high stability of foams obtained from mixtures of surfactants can be explained by the formation of mixed structured layers from the surface-active associates, promoting the thickening of foam films. The ratio of polymer mixtures was optimized (keratin (15%)-albumin (1%) (1:1)) to produce high-quality foaming agents. The foam parameters such as surface tension, capillary pressure of the Plateau-Gibbs channels, radii of curvature, critical micelle concentration, and relative viscosity were defined. The high surface activity and foam stability corresponds to a pH close to the isoelectric state of the proteins. This occurs due to the conformational changes of macromolecules of the protein at the liquid-gas interface, forming particles of colloidal size. Full article
(This article belongs to the Special Issue Selected Papers from Bubble & Drop 2017)
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Open AccessFeature PaperArticle Multilayer Adsorption of Heptane Vapor at Water Drop Surfaces
Colloids Interfaces 2017, 1(1), 8; https://doi.org/10.3390/colloids1010008
Received: 16 November 2017 / Revised: 30 November 2017 / Accepted: 1 December 2017 / Published: 4 December 2017
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Abstract
The measured dynamic surface tension of a water drop in air saturated by heptane vapor shows a sharp decrease from about 60 mN m−1 to 40 mN m−1, and less after a certain adsorption time. The observed adsorption kinetics is
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The measured dynamic surface tension of a water drop in air saturated by heptane vapor shows a sharp decrease from about 60 mN m−1 to 40 mN m−1, and less after a certain adsorption time. The observed adsorption kinetics is analyzed by a theoretical model based on multilayer adsorption of alkanes from the vapor phase at the water surface. The model assumes a dependence of the kinetic coefficients of adsorption and desorption on the surface coverage and in equilibrium it reduces to the classical Brunauer–Emmett–Teller adsorption isotherm. The calculated time dependencies of adsorption and surface tension agree well with experimental data and predict a five-layer adsorption of heptane. Full article
(This article belongs to the Special Issue Selected Papers from Bubble & Drop 2017)
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Graphical abstract

Open AccessFeature PaperArticle Surface Tension Measurements with the Drop Profile Analysis Tensiometry—Consideration of the Surfactant Mass Balance in a Single Drop
Colloids Interfaces 2017, 1(1), 1; https://doi.org/10.3390/colloids1010001
Received: 3 August 2017 / Revised: 23 August 2017 / Accepted: 29 August 2017 / Published: 1 September 2017
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Abstract
In drop profile analysis tensiometry, the ratio of drop surfaces area S to volume V is large, i.e., S/V >> 1. In such a case, the concentration of a surfactant within the drop bulk decreases due to adsorption at the drop surface. In
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In drop profile analysis tensiometry, the ratio of drop surfaces area S to volume V is large, i.e., S/V >> 1. In such a case, the concentration of a surfactant within the drop bulk decreases due to adsorption at the drop surface. In contrast, in bubble profile analysis tensiometry, we have S/V << 1 so that depletion due to adsorption is negligible. A protocol is presented to determine the correct adsorption parameters of surfactants from surface tension data measured by bubble and drop profile analysis tensiometry. The procedure is applied to experimental data measured for selected surfactants of different adsorption activities: C10OH, CTAB, Tween 20, and the equimolar mixture SDS + DoTAB. The results show that for surfactants with higher surface activity, the differences between the surface tensions measured with the drops and bubbles profile analysis tensiometry, respectively, are larger, while for less surface-active surfactants, such as SDS, the results obtained from drop and bubble profile experiments are very close. The correction procedure is based on the same set of adsorption parameters used to fit both the experimental data obtained from drop-based measurements (which involve the depletion effects) and those data measured in a way that depletion effects are negligible. Full article
(This article belongs to the Special Issue Selected Papers from Bubble & Drop 2017)
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Review

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Open AccessReview The Use of Polymer and Surfactants for the Microencapsulation and Emulsion Stabilization
Colloids Interfaces 2017, 1(1), 3; https://doi.org/10.3390/colloids1010003
Received: 19 September 2017 / Revised: 13 October 2017 / Accepted: 18 October 2017 / Published: 29 October 2017
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Abstract
Polymer/surfactant mixtures have a wide range of industrial and technological applications, one of them being the use in microencapsulation and emulsion stabilization processes. These mixtures are able to form adsorption layers at the surface of oil droplets and so affect the emulsion stability,
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Polymer/surfactant mixtures have a wide range of industrial and technological applications, one of them being the use in microencapsulation and emulsion stabilization processes. These mixtures are able to form adsorption layers at the surface of oil droplets and so affect the emulsion stability, which depends on the polyelectrolyte/surfactant nature, concentrations ratio, method of the emulsification, etc. Polyelectrolytes alone show low surface activity in contrast to surfactants, which adsorb at the water/oil interface, making the droplets charged, but they are insufficient to stabilize emulsions. When an oppositely-charged polymer is added to the surfactant solution, a steric barrier is formed, which prevents coalescence and enhances the stability. The present review is devoted to the recent studies of the use of polymer/surfactant mixtures for the encapsulation of active ingredients and stabilization of single and double emulsions. Active ingredients are added to the oil phase prior to emulsification so that any subsequent dissolution of the core, like in other encapsulation protocols, can be omitted. By measuring the interfacial tension and dilational rheology it is possible to find optimum conditions for the emulsion formation and hence for encapsulation. Therefore, such systems have become a prominent approach for the encapsulation of active ingredients. Full article
(This article belongs to the Special Issue Selected Papers from Bubble & Drop 2017)
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