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Gas-Phase Induced Marangoni Flow Causes Unstable Drop Merging
Peyman Rostami1,2, Benedikt B Straub2, Günter K Auernhammer1,2
1Leibniz-Institut für Polymerforschung Dresden , e. V. Hohe Straße 6 , 01069 Dresden , Germany.
Langmuir : the ACS Journal of Surfaces and Colloids
|December 12, 2019
Summary
Driven wetting films become unstable through fingering instability when Marangoni stress is applied. Spreading velocity controls this instability, creating distinct regimes shown in a stability diagram.
Area of Science:
- Fluid dynamics
- Surface science
- Interfacial phenomena
Background:
- Drop merging is crucial in processes like rain and coating applications.
- Inkjet printing involves merging liquids with differing surface tensions on substrates.
- Stable wetting films can form when one liquid drop covers another, depending on surface tensions.
Purpose of the Study:
- To investigate the dynamics of driven wetting films.
- To identify conditions leading to instability in these films.
- To explore the role of Marangoni stress in driving wetting film instability.
Main Methods:
- Studying driven wetting films under Marangoni stress.
- Observing fingering instability in various liquid combinations.
- Controlling vapor concentration via spreading velocity to map instability characteristics.
Main Results:
- Wetting films become unstable via fingering instability when driven by Marangoni stress.
- Marangoni flow, induced by lower surface tension liquid vapor, pulls the wetting film.
- Instability is dependent on spreading velocity, with distinct regimes identified in a stability diagram.
Conclusions:
- Spreading velocity is a key control parameter for fingering instability in driven wetting films.
- A simplified 1D model explains how spreading velocity influences vapor concentration profiles.
- Marangoni flow strength is linked to the exposure time of drops to vapor concentration gradients.
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