Phase Field Modeling and Verification of a Wetting Model for Hydrophilic and Hydrophobic Surfaces

Open Access
Author:
Calogero, Lauren Michelle
Graduate Program:
Mechanical Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
March 21, 2016
Committee Members:
  • Michael Tonks, Thesis Advisor
Keywords:
  • phase field
  • wetting
  • roughness
  • hydrophobic
  • hydrophilic
  • superhydrophobic
  • Wenzel
  • microstructure
  • MOOSE
  • contact angle
Abstract:
Wetting properties of surfaces are of interest due to their potential applications in many fields. Differences in surface tension between liquid and solid can allow hydrophilicity, attraction to liquid, or hydrophobicity, repelling liquid. In this study, a phase field model was implemented to study the effects of varied surface geometry on wetting properties. Of particular interest are superhydrophobic surfaces, or surfaces with a contact angle exceeding 150°. This behavior is due to surface roughness. Such surfaces can be fabricated in a number of ways, including top-down and bottom-up approaches. Many surface geometries have been theorized, modeled, and tested for the purpose of creating a more effective superhydrophobic surface. First, a 2-D phase field model was implemented in MOOSE (Multiscale Object-Oriented Simulation Environment) for a flat surface. Results were related to real materials for the Wenzel (fully wetted) and Cassie-Baxter (resting on a layer of air) states. The model’s accuracy was then verified for a pillared surface using the Cassie-Baxter and Wenzel formulas and experimental data. After this verification, other patterned surfaces were created in MOOSE to relate microstructures’ shape, size, and wetting state to contact angle. Other patterns included raspberry-shaped particle-covered surfaces and a triangular saw tooth pattern.