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Size limit for particle-stabilized emulsion droplets under gravity
J W Tavacoli1, G Katgert, E G Kim
1School of Physics and Astronomy, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JZ, United Kingdom.
Physical Review Letters
|September 26, 2012
Summary
Emulsion droplets stabilized by particles become unstable when they exceed a size threshold due to gravity. Particle ejection occurs until remaining particles are lighter than the binding force of a single particle, forming a stable shape.
Area of Science:
- Colloid and Interface Science
- Fluid Dynamics
- Materials Science
Background:
- Emulsion droplets are crucial in various industries.
- Particle stabilization of emulsions is a common technique.
- Understanding droplet stability limits is essential for process control.
Purpose of the Study:
- To investigate the critical size limit for particle-stabilized emulsion droplet stability.
- To identify the mechanisms driving droplet instability and particle ejection.
- To determine the conditions for achieving stable configurations.
Main Methods:
- Experimental observation of emulsion droplets stabilized by colloidal and supracolloidal particles.
- Direct visualization of particle ejection events at the droplet interface.
- Analysis of forces, including gravity and interfacial binding forces.
- Investigation of the role of droplet surface curvature.
Main Results:
- Droplet instability is observed beyond a gravity-defined size threshold.
- Particle ejection from the droplet base occurs, with decreasing numbers of particles involved over time.
- A stable 'acorn-like' configuration is reached when particle weight is less than the binding force of a single particle.
- Droplet surface curvature significantly promotes particle ejection.
Conclusions:
- Gravity is a key factor in the instability of particle-stabilized emulsion droplets.
- The ejection process leads to a stable state governed by interfacial forces.
- Surface curvature plays a critical role in initiating particle expulsion.
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