title: Mechanical Characterization of Ultralow Interfacial Tension Oil-in-Water Droplets by Thermal Capillary Wave Analysis in a Microfluidic Device.
abstract: Measurements of the ultralow interfacial tension and surfactant film bending rigidity for micron-sized heptane droplets in bis(2-ethylhexyl) sodium sulfosuccinate-NaCl aqueous solutions were performed in a microfluidic device through the analysis of thermally driven droplet interface fluctuations. The Fourier spectrum of the stochastic droplet interface displacement was measured through bright-field video microscopy and a contour analysis technique. The droplet interfacial tension, together with the surfactant film bending rigidity, was obtained by fitting the experimental results to the prediction of a capillary wave model. Compared to existing methods for ultralow interfacial tension measurements, this contactless, nondestructive, all-optical approach has several advantages, such as fast measurement, easy implementation, cost-effectiveness, reduced amount of liquids, and integration into lab-on-a-chip devices.
authors.affiliation: Department of Chemistry, Imperial College London , London SW7 2AZ, U.K.
authors.forename: Guido
authors.initials: G
authors.lastname: Bolognesi
authors.affiliation: Department of Chemistry, Imperial College London , London SW7 2AZ, U.K.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Saito
authors.affiliation: Department of Chemistry, Imperial College London , London SW7 2AZ, U.K.
authors.forename: Arwen I I
authors.initials: AI
authors.lastname: Tyler
authors.affiliation: Central Laser Facility, STFC , Harwell Oxford OX11 0QX, U.K.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Ward
authors.affiliation: Department of Chemistry, Durham University , Durham DH1 3LE, U.K.
authors.forename: Colin D
authors.initials: CD
authors.lastname: Bain
authors.affiliation: Department of Chemistry, Imperial College London , London SW7 2AZ, U.K.
authors.forename: Oscar
authors.initials: O
authors.lastname: Ces