Challenges in Design and Manufacturing of Superhydrophobic and Superoleophobic Surfaces

K.Y. Law
Research and Innovative Solutions, US

Keywords: superhydrophobicity, superoleophobicity, design parameters, manufacturing, fabrication methods

Summary:

Using model pillar array surfaces, we show that the basic design parameters to create a superoleophobic surface are to have a textured surface with a re-entrant structure and an oleophobic surface coating. In this paper, critical functional requirements to design a robust superoleophobic surface are described. Although the critical functional requirements will depend on the application, the list should include liquid repellency, adhesion, hysteresis, wetting breakthrough pressure and abrasion resistance. Using model surfaces fabricated by photolithography and surface fluorination as well as Surface Evolver simulation and mechanical modeling study, design parameters that will allow the surface to meet the functional requirements are: contact angle of the smooth surface, geometry of the re-entrant structure, the solid area fraction, the diameter of the pillar and the pillar height. The design latitude space is found to be related to the pressure for a given application, the higher the external pressure, the narrower the latitude space will be. Fabrication methods to make superoleophobic surfaces include the bottom-up and top-down approaches will be reviewed and the use of some of the procedures as manufacturing methods is discussed. The challenge in manufacturing large area, large scale superoleophobic surface is highlighted.