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Updated: May 9, 2025
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Measuring the Interaction Force Between a Droplet and a Super-hydrophobic Substrate by the Optical Lever Method
Published on: June 14, 2019
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Simultaneous measurement of interaction force and liquid film thickness between two approaching droplets using
Yijing Jin1, Han Zhou1, Shan Jing1
1Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084, China.
Journal of Colloid and Interface Science
|May 3, 2025
Summary
Researchers developed a new apparatus to measure dynamic droplet interactions and film drainage. Stronger interaction forces prolong drainage, while initial dimples shorten it, revealing new phenomena.
Area of Science:
- Colloid and Interface Science
- Fluid Dynamics
- Physical Chemistry
Background:
- Understanding droplet-droplet interactions is vital for various scientific fields.
- Current methods lack the ability to measure dynamic inter-droplet interaction forces.
- A novel measurement approach is necessary to study dynamic droplet interactions.
Purpose of the Study:
- To develop and validate a novel apparatus for measuring dynamic inter-droplet interaction forces.
- To investigate the influence of operational conditions on the film drainage process between droplets.
- To analyze the spatiotemporal evolution of film thickness during droplet interactions.
Main Methods:
- Designed and custom-developed an apparatus integrating optical interferometry and the interface probe method.
- Simultaneously measured time-dependent inter-droplet interaction forces and film thickness.
- Investigated dynamic interactions between aqueous droplets in an organic medium.
Main Results:
- Measured liquid film thickness distribution aligns with Reynolds lubrication theory.
- Measured inter-droplet interaction forces are consistent with theoretical calculations.
- Observed a novel curvature inversion phenomenon in the liquid film, deviating from existing models.
Conclusions:
- The developed apparatus accurately measures dynamic inter-droplet interaction forces and film thickness.
- Initial dimple prominence and interaction forces significantly affect film drainage times.
- The observed curvature inversion phenomenon may result from surfactant redistribution and interface renewal.
