Study on biomimetic preparation of shell surface microstructure for ship antifouling

Abstract

The attachment of marine fouling organisms is harmful to any marine structure such as ship hulls, fishing nets, jetties and platforms. The surface microstructure of materials has a great influence on its antifouling performance. The surfaces of some types of shells are very clean without fouling even though they are in seawater for long time, which can be used as biomimetic objects for antifouling. In order to study ship green antifouling technology based on biomimetic shell microstructure, three common marine shells Dosinia japonica, Gafrarium pectinatum and Mimachlamys nobilis were selected to study the relationship between the shell surface microstructure and the antifouling performance. Taking the outside surface of the three shells as the bio-replication templates, polydimethylsiloxane (PDMS) as female mold, E44 epoxy resin and polyurethane (PU) as male mold materials, the replicas were prepared by means of the bio-replicated forming method. The surfaces were measured with the LI-3 contact surface profilometer and the form errors of measuring data were then separated by two-dimensional biorthogonal wavelet transform. Seven three-dimensional surface parameters, Sa, Sq, Ssk, Sku, Sy, Sz and Stdi were calculated to compare each replica with the original surface. The results showed that E44 epoxy resin and PU accurately reproduced the shell surface microstructure with the relative errors mostly lower than 10%. The replica accuracy of the epoxy resin was a little bit better than that of PU for fine tiny microstructure. Fouling tests with E44 epoxy resin replicas were conducted in laboratory for 4 weeks. The content of chlorophyll-a of Nitzschia closteriums was then used to characterize the antifouling ability of the replicas. The chlorophyll-a content results and the contact angle analysis showed that the E44 replica of D. japonica had the best antifouling ability while the E44 replica of M. nobilis had the worst antifouling ability among three kinds of E44 replicas.