Design and Development of Super Water- and Oil-Repellent Surfaces by Topographic Manipulation

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Abstract Design and Development of Super Water- and Oil-Repellent Surfaces by Topographic ManipulationDi Gao and Hsin-Hua HuDepartment of Chemical and Petroleum Engineering and Department of Mechanical EngineeringUniversity of Pittsburgh, Pittsburgh, PA 15261Super-hydrophobic and oleophobic surfaces with contact angles of greater than 150 for water and oil, respectively, are of great interest for applications in green construction, self-cleaning products, and microfludic systems. Typically, a contact angle of greater than 90 on the flat surface of a material is required to further increase the contact angle by tuning the surface roughness. However, the proposed research aims to develop super-hydrophobic/oleophobic surfaces from intrinsically hydrophilic/oleophilic materials (with contact angles of less than 90 on their flat surfaces) by manipulating the surface topography in micro- and nano-scales. This will be realized by constructing surfaces with designed topographies consisting of overhangs. The overhangs will induce the formation of fakir liquid droplets by providing positions to support the liquid sitting above a composite surface of solid and air, which will result in a macroscopic hydrophobicity/oleophobicity. In addition, hierarchical topographic configurations will be designed and fabricated to further increase the hydrophobicity/oleophobicity of the constructed surfaces. Dynamic properties of liquids (such as sliding, creeping, rolling, and bouncing) on the constructed surfaces will also be investigated. This project will integrate research and education by increased participation of underrepresented groups, and outreach to elementary schools and exposure of young students to surface science.