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On the dynamic contact angle of capillary-driven microflows in open channels
Jodie C Tokihiro1, Anika M McManamen1, David N Phana1
1Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195, United States.
Biorxiv : the Preprint Server for Biology
|May 10, 2023
Summary
Fluid penetration in microfluidics requires a dynamic contact angle, not a static one, especially in open channels. The molecular-kinetic theory accurately predicts this dynamic angle for various liquids.
Area of Science:
- Physical Chemistry
- Fluid Dynamics
- Materials Science
Background:
- The Lucas-Washburn-Rideal (LWR) law, fundamental to capillary microfluidics, assumes a constant contact angle during fluid penetration.
- Experimental evidence indicates lower liquid velocities than predicted by the LWR law, attributed to a velocity-dependent dynamic contact angle.
Approach:
- Investigated dynamic contact angles in open channel configurations using experimental data.
- Utilized a range of aqueous and organic liquids with a Polymethyl methacrylate (PMMA) substrate.
- Analyzed fluid penetration dynamics, focusing on the early stages of the viscous regime.
Key Points:
- A dynamic contact angle is crucial for explaining fluid penetration in the early viscous regime at high velocities.
- Open channel configurations, featuring a free surface, amplify the significance of the dynamic contact angle.
- The molecular-kinetic theory (MKT) demonstrated superior accuracy in predicting dynamic contact angle effects in open channels.
Conclusions:
- Dynamic contact angles are essential for accurate modeling of fluid penetration in microfluidic systems, particularly in open channels.
- The molecular-kinetic theory provides a robust framework for understanding and predicting dynamic contact angle phenomena in capillary-driven flows.
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