Jump to main content
Jump to site search

Issue 34, 2012
Previous Article Next Article

A criterion to assess the impact of confined volumes on surfactant transport to liquid–fluid interfaces

Author affiliations

Abstract

When dissolved surfactant adsorbs at an interface, the bulk concentration decreases. If the initial concentration is low or the interfacial area large, the concentration decrease can be significant, and the solution depleted. Although depletion is not a new phenomenon, properly accounting for it requires a global mass conservation constraint in addition to a mass transport model. The emergence of new applications involving adsorption in finite volumes and with large surface areas, including micro- and nanoscale droplet formation, has introduced new scenarios in which depletion can be significant but complex to analyze. The purpose of this paper is to develop simple criteria to allow practitioners in these applications to rapidly and easily assess the potential impact of depletion. We use a global mass balance to show that two dimensionless parameters fully describe the role of depletion in both equilibrium surface properties and timescales to reach equilibrium. The dimensionless parameters represent the potential mass lost to the interface, denoted ζ, and the surface activity of the surfactant, denoted f. Characteristic transport timescales are shown to be a function of the finite geometry. A scaling analysis is developed for the case of surfactant dissolved inside a spherical drop, and compared with that of a finite spherical shell. The analyses developed here lead to simple criteria that are useful even when the surfactant properties are not well characterized or a full transport analysis is difficult. The criteria can be generalized to adsorption at solid surfaces.

Graphical abstract: A criterion to assess the impact of confined volumes on surfactant transport to liquid–fluid interfaces

Back to tab navigation

Supplementary files

Article information


Submitted
25 Feb 2012
Accepted
21 Jun 2012
First published
23 Jul 2012

Soft Matter, 2012,8, 8917-8925
Article type
Paper

A criterion to assess the impact of confined volumes on surfactant transport to liquid–fluid interfaces

N. J. Alvarez, L. M. Walker and S. L. Anna, Soft Matter, 2012, 8, 8917
DOI: 10.1039/C2SM25447F

Social activity

Search articles by author

Spotlight

Advertisements