Characterization of Oleophobic Functional Surfaces Fabricated by Thermal Imprinting Process

Abstract

Extended Abstract Nanostructure is the prerequisite to obtain an appropriate surface roughness for the superhydrophobicity or oleophobicity. Synthetic surfaces with nano-sized bumps have been recently developed based on low-energy surface and multiscale roughness by various nanotechniques [1]. Especially, antifouling, deicing, antibacterial, and self-cleaning surfaces are important for improving the energy efficiency of building, automobile, medical devices, and household care [2]. During the past two decades, superhydrophobic nanostructures and nanocoatings that are inspired by the lotus-leafs effect have been extensively studied. However, studies on the oloephobic surfaces were paid less attention. Therefore, it is a challenge to create functional surfaces which completely resist wetting not only by water, but also by organic liquids such as oils [3]. In this work, a study on fabrication and characterization of oleophobic (repellent to oil) surface using thermal imprint lithography is conducted. For thermal imprinting process, a nickel (Ni) stamp with pillar-array was fabricated. During the imprint lithography, the PMMA (polymethyl methacrylate) substrate was prepared and heated above the glass transition temperature. As a result, the micro-patterned PMMA sheet was successfully formed [Fig. 1]. By application of fluoride coating (DURASURF, HARVES. Co.) and polymer nano-particles stacking on the micro-patterned PMMA sheet, a surface modification was carried out. Thus, the hierarchical complex surfaces which have superhydrophobic and oleophobic properties with complex nano-particles on micro-patterns were created. This hierarchical structure played an important role in oil-repellent properties. As a result, the imprinted surface from nickel stamp showed contact angle around 150° for water and 118° for hexadecane. This method can be applicable for a variety of applications such as self-cleaning, antifouling, and antifrosting. Furthermore, we will discuss the mechanism of creating an oleophobic coating in details.