Influence of Surface Topography on Marine Biofouling

Abstract

Marine biofouling, associated with the accumulation of marine colonizers on submerged surfaces, has been a longstanding problem. Among different surface properties, cell substrate interaction is strongly influenced by surface topographies. Therefore, in this work responses of representative marine fouling species were investigated in relation to different topographies. The settlement of zoospores of Ulva linza was explored on a hot-embossed honeycomb gradient. The highest settlement was found on microstructures with a similar or larger size than spores. Spore settlement density correlated with the Wenzel roughness of the topographies and ‘kink sites’ resembled preferred attachment positions. Following the gradient study, different settlements of cells of Navicula incerta, Ulva zoospores, and cyprids of B. improvisus were observed on soft-casted discrete honeycombs with the feature size as the only variable. The correlation between the ‘attachment point theory’ and the diatom attachment was in line with the literature. Settlement of spores deviated from the guideline of Wenzel roughness mainly due to the gregarious settlement on PDMS substrates, while the settlement of cyprids could be correlated with both Wenzel roughness and the interaction between sensory structures and comparably sized microtopographies. Furthermore, tapered microstructures with different feature spacings and aspect ratios were prepared via hot embossing and hot pulling to avoid unfavorable corners and to minimize the surface contact area. Topographic preferences of Navicula diatoms and Ulva spores during settlement were proven to be dominated by the ‘attachment point theory’ and Wenzel roughness, respectively. Topographic cues guiding the settlement turned out to be complicated as they were related to both, topographies and fouling species. As effective antifouling strategies, the combined effect of a variety of surface properties seems appropriate. Along these lines, the concept of slippery liquid-infused porous surfaces (SLIPS), which combined both surface lubricity and topographies, were tested against fouling under both laboratory and field conditions. Immersion tests suggested a correlation between the stability of slippery coatings in seawater and fouling resistance efficacy. On stable slippery surfaces, settlement of Ulva spores and Balanus amphitrite cyprids was remarkably reduced. Although both marginal fouling-release and poor field performance indicated the requirement of significant improvement of such coatings for practical applications, the fouling resistant potential of the SLIPS concept was demonstrated.