Is the surface tension of a liquid droplet stable?

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SUMMARY

The surface tension of water at room temperature is approximately 72 mN/m; however, this value is not uniform across a droplet due to varying curvature, which affects Laplace pressure. Surface contamination, surfactants, or solutes can significantly reduce surface tension. Additionally, interfacial energy remains constant despite spatial gradients, which can lead to phenomena such as Marangoni flow when temperature or concentration gradients are present. Understanding these factors is crucial for accurately assessing the stability of liquid droplets.

PREREQUISITES
  • Understanding of surface tension and its measurement
  • Familiarity with Laplace pressure and curvature effects
  • Knowledge of interfacial energy and its role in phase interactions
  • Basic principles of Marangoni flow and its causes
NEXT STEPS
  • Research the effects of surfactants on surface tension in liquids
  • Explore the mathematical formulation of Laplace pressure in curved surfaces
  • Investigate the principles of Marangoni flow and its applications
  • Study the impact of gravitational fields on droplet stability and curvature
USEFUL FOR

Researchers in fluid dynamics, chemists studying surface phenomena, and engineers working with emulsions or coatings will benefit from this discussion.

lionelwang
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Hi all,

Typically, we know that the surface tension for water is about 72mN/m at RT. so do this mean that the surface tension over the whole droplet is exactly the same? Moreover, we know that the Laplace pressure may be different over the whole droplet as the curvature in different parts might be different. How to explain those phenomena?
Waits for your wisdom, and thanks for any help!
 
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the value you quote is for pure water- surface contamination, surfactants, or other solutes will drastically lower the value.

The curvature is allowed to vary with, for example, height in a gravitational field (hydrostatic pressure head). This does not change the interfacial energy, which is a property of the two phases.

The interfacial energy can support spatial gradients (Marangoni flow, for example) if there is a temperature or concentration gradient.

does that help?
 

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