Microtextured surfaces: towards macrofouling resistant coatings

Fouling by marine organisms attached to ships' hulls is a serious problem for the shipping industry because it causes added drag which increases fuel consumption. In this study, the effect of micro texture on the biofouling resistance of low surface energy RTV silicones (PDMS) has been investigated. Surface microtexture in the the range of 50-100 mu m was achieved by molding silicones against various mesh structures. The surfaces were characterized with regard to chemical composition using electron spectroscopy for chemical analysis (ESCA); surface topography was analyzed using scanning electron microscopy (SEM) and atomic force microscopy (AFM), and wetting behavior was evaluated using contact angle measurements. It was found that the surface chemistry was not affected by the molding procedure and the surface texture proved to be regular and free from defects, with a surface free energy of 25.5 mN m(-1). Above a certain degree of surface roughness, the water contact angle hysteresis decreased, which is characteric for composite surfaces according to the theories developed by Cassie and Baxter. Two-week field exposure on the west coast of Sweden showed that the microtextured PDMS surfaces were significantly less fouled by the barnacle Balanus improvisus than the smooth control PDMS surfaces.