Hydrophobicity of curved microstructured surfaces

• Published in: Journal of micromechanics and microengineering 2010-02, Vol.20 (2), p.025018-025018
• Main Authors: Cannon, A H, King, W P
• Format: Article
• Language: English
• Subjects: Applied sciences; Arrays; Condensed matter: structure, mechanical and thermal properties; Curvature; Droplets; Electronics; Exact sciences and technology; Hydrophobicity; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Liquids; Mathematical analysis; Mechanical engineering. Machine design; Mechanical instruments, equipment and techniques; Microelectronic fabrication (materials and surfaces technology); Micromechanical devices and systems; Microstructure; Physics; Polymers; Precision engineering, watch making; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Solid-fluid interfaces; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Wetting
• ISSN: 0960-1317; 1361-6439
• DOI: 10.1088/0960-1317/20/2/025018

This paper presents measurements and models for how the macroscopic curvature of microstructured polymers affects hydrophobicity. Flexible polymer substrates were fabricated with arrays of regular microstructures. The interaction of liquid drops with these surfaces was analyzed for flat substrates and substrates flexed into either positive or negative cylindrical shapes. Liquid droplet static contact angle and dynamic slide angle were measured for a range of surfaces. An increase in substrate curvature corresponded with decreased slide angle for liquid droplets suspended on the surface asperities. This phenomenon is investigated in terms of solid--liquid contact line and the periodicity of surface microstructures. We present a model that can be used to understand the observed phenomena and to design microstructure geometries for hydrophobicity.