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Microscopic and macroscopic structure of the precursor layer in spreading viscous drops
H Pirouz Kavehpour1, Ben Ovryn, Gareth H McKinley
1Hatsopoulos Microfluids Laboratory, Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Physical Review Letters
|November 13, 2003
Summary
We observed liquid spreading on surfaces, measuring microscopic and macroscopic flow scales. Our findings quantitatively match theoretical predictions for van der Waals liquids.
Area of Science:
- Fluid dynamics
- Surface science
- Physical chemistry
Background:
- Understanding liquid spreading on surfaces is crucial in various scientific and industrial applications.
- The dynamics of thin liquid films involve complex interactions across multiple length scales.
Purpose of the Study:
- To investigate the spreading behavior of viscous, nonvolatile liquids on smooth horizontal substrates.
- To simultaneously measure microscopic and macroscopic flow scales and the transitional region during wetting.
Main Methods:
- Utilized a phase-modulated interference microscope with a wide dynamic range.
- Enabled simultaneous measurement of inner (microscopic) and outer (macroscopic) flow scales.
- Analyzed the precursor wetting film and apparent contact angle.
Main Results:
- Successfully measured both microscopic and macroscopic length scales of liquid spreading.
- The apparent contact angle and lateral scale of the wetting film were quantitatively determined.
- Measurements showed excellent agreement with theoretical predictions for van der Waals liquids.
Conclusions:
- The study provides a comprehensive understanding of liquid spreading dynamics across different scales.
- Experimental results validate theoretical models for van der Waals liquid behavior.
- The employed microscopy technique is effective for studying thin film dynamics.