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Layered droplet microstructures in sheared emulsions: finite-size effects
Jai A Pathak1, Melissa C Davis, Steven D Hudson
1Polymers Division, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899-8544, USA. Jai.Pathak@nist.gov
Journal of Colloid and Interface Science
|December 31, 2002
Summary
Confinement influences emulsion microstructure under shear, forming layers that change with shear rate and droplet size. Droplet interactions and wall effects dictate layering and morphology, including stable pearl-necklace structures.
Area of Science:
- Colloid and Surface Science
- Rheology
- Microfluidics
Background:
- Understanding confined emulsions is crucial for industrial processes.
- Shear flow significantly alters droplet behavior and microstructure.
Purpose of the Study:
- Investigate how confinement affects steady-state microstructure in sheared emulsions.
- Determine the influence of shear rate and composition on emulsion morphology.
Main Methods:
- Utilized droplet velocimetry to track droplet movement.
- Analyzed microstructure under varying shear rates and mixture compositions.
- Developed a morphology diagram based on mass fraction and shear rate.
Main Results:
- Droplets organized into discrete layers, decreasing from two to one layer with lower shear rates.
- Layering and composition profiles are influenced by droplet collisions, migration, and packing.
- Observed stable pearl-necklace chain structures and strings of the suspended phase over a broad composition window.
Conclusions:
- Confinement and shear critically control emulsion microstructure.
- Droplet interactions and wall effects are key drivers of observed layering and morphology.
- A morphology diagram effectively summarizes phase behavior in confined sheared emulsions.