Faculty Project Proposal Summary
Calendar Year 2014 Program
Faculty Name & Department/School: Travis Walker, CBEE
Research Project Title: Measuring dynamic interfacial tension by two-drop capillary diffusion
Drops and jets of liquids that are miscible with the surrounding bulk liquid are present in many processes from cleaning surfaces with the aid of liquid soaps to the creation of biocompatible implants for drug delivery. Although the interactions of immiscible drops and jets show similarities to miscible systems, the small, transient interfacial tension associated with miscible systems create distinct outcomes such as intricate droplet shapes, break-up resistant jets, and spreading sessile drops.
The transient, interfacial tension is central to the evolution in the shape of droplets and jets of liquids translating within a medium in which they are miscible. Yet, measurement of this property is challenging not only because the values are small but also because they diminish in time as diffusion proceeds and the two liquids ultimately mix. For that reason, the majority of published experimental reports on this problem do not offer measurements of this property.
This project proposes using a capillary tube filled with a fluid (A) that is submerged into two other different fluids (B & C) at each end. If A is immiscible with both B and C, then the ratio of the size of the radii of curvature of the small hemispherical droplet protruding into their respective baths will be equal to the ratio of their respective interfacial tensions with A. If A is immiscible with B but miscible with C, then the dynamic interfacial tension between A and C can be measured by tracking the change in the ratio of the radii of curvature and scaling by the known interfacial tension between A and B. Thus, a simple three-fluid experiment will allow for the measurement of the dynamic interfacial tension of a hemispherical drop.
Further efforts could then be made to understand how various materials affect the interfacial tension of a system and possibly how surfactants migrate to the interface.
What skills will students obtain in this project?
Students will work on technique development by freely thinking about their design, leveraging their intuition and ingenuity to make useful measurements in the lab. They will obtain a theoretical background in capillarity and diffusion as well as an introduction to overall fluid mechanics. Students will also learn basic numerical analysis and image processing through Matlab programming.
Student research tasks:
Develop novel system to measure radii of curvature of one fluid in two other different fluids, making use of the ideas described in the Project Overview section.
Run experiments of a various three-fluid systems (possibly water-glycerol-mineral oil), recording time sequences of the dynamical process.
With help from either the PI or a graduate student, develop an analysis code for extracting dynamic data.
Analyze the data from the various systems, interpret the results, and report the findings, while re-evaluating the initial experimental apparatus and techniques.
Number of hours per week expected of student:
I would like to see the student in the lab at least four to six hours per week.
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Download student application HERE
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