Design Parameters for “Robust” Superoleophobicity Surfaces

K-Y Law, H. Zhao, K-C Park
Xerox Corporation, US

Keywords: superoleophobicity, wetting, robustness, design parameters

Summary:

Earlier we reported the fabrication of a model superoleophobic surface comprising ~3-micron diameter pillar arrays on Silicon. Results showed that both surface fluorination and the re-entrant geometry are crucial in achieving the superoleophobicity with hexadecane contact angle at >150 deg and a sliding angle at ~10 deg. Here, we report investigation on the effects of pillar height, size and spacing on the surface properties. Results showed that while both static and advancing contact angles remain at >150 deg as the pillar size and spacing vary, the receding contact angle, sliding angle and hysteresis are found to be sensitive to these structure changes. The receding angle decreases, and sliding angle & hysteresis increases as the solid area coverage increases. On the other hand, surface superoleophobicity remains as the height of the pillar decreases from about 7 to 1 micron. Surface Evolver simulation was used to model the location of the contact line and its robustness against external pressure. The abrasion resistance of the pillar array surface was assessed via mechanical modeling and nanoindenter measurement. The design space for fabricating superoleophobic surface that is robust against wetting and mechanical abrasion is discussed.