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Constrained Drop Surfactometer for Studying Interfacial Structure and Rheology.

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Title:Constrained Drop Surfactometer for Studying Interfacial Structure and Rheology.
Authors:Yang, Jinlong
Contributors:Mechanical Engineering (department)
Keywords:axisymmetric drop shape analysis
constrained drop surfactometer
Neumann number
surface dilational rheology
surface tension
Date Issued:Dec 2017
Publisher:University of Hawaiʻi at Mānoa
Abstract:Measurements of surface tension and interfacial rheology of liquid-fluid surfaces play an
important role in a variety of scientific and industrial fields, such as smart material, thin film,
soft matter, microfluidics, and biophysics. Being a miniaturized experimental platform for
studying surface phenomena, droplets hold great advantages over the traditional experimental
methods, such as the classical Langmuir trough, in determining surface tension and interfacial
rheological properties. The focus of this thesis was to develop a novel droplet-based
experimental platform called the constrained drop surfactometer (CDS) for studying surface
tension and interfacial rheology. Axisymmetric drop shape analysis (ADSA) was used as a
numerical algorithm to determine the dynamic surface tension as a function of time and surface
area variations. We first proposed a new dimensionless parameter, called the Neumann number,
N e   g R0 H /  , to replace the classical Bond number for evaluating the accuracy of ADSA
upon reducing drop volume. We then developed a closed-loop ADSA (CL-ADSA) algorithm for
determining and controlling droplet parameters, including the volume, surface area, and surface
tension, in real-time. With the CL-ADSA, the CDS was transformed from a traditional surface
tension measurement methodology to a sophisticated experimental platform for manipulating
millimeter-sized single droplets in real-time. We have demonstrated the accuracy, robustness,
versatility, and automation of this droplet manipulation technique. Finally, we engaged the
combination of CDS and CL-ADSA in studying interfacial rheology. Understanding the
interfacial rheology of complex fluids plays a central role in a range of applications such as food
processing, detergency, coating, cosmetic, and pharmacology. For the first time, our
methodological advance permitted direct control of surface area oscillated in a sinusoidal pattern,
thus resulting in a precise evaluation of the surface dilational rheological properties of complex fluids, including surfactants and proteins. Our results showed that the CDS, together with the
CL-ADSA, holds great promise for advancing the study of interfacial structure and rheology.
Description:Ph.D. Thesis. University of Hawaiʻi at Mānoa 2017.
Rights:All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.
Appears in Collections: Ph.D. - Mechanical Engineering

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