Research On Adhesion Mechanism And Antifouling Technologies Of A Marine Benthic Diatom

Because of biofouling, worldwide fuel consumption of ships is increased, and theship hull corrosion and maintenance costs are also increased, causing a great financiallosses and extra energy consumptions in the marine industries. Therefore, research onthe antifouling technology is of great importance in both theoretical aspects andpractical applications. This paper studies the adhesion mechanism of a representativebenthic diatom Navicula sp. through experiments and theoretical calculations. Based onthese understandings, an effective and environmentally friendly antifouling coatingbased on silicone elastomer and colored phosphor powder is proposed.According to the diatom initial settlement experiments, the approach processbetween suspending diatom and surfaces is researched. It shows that there is significantdiurnal positive buoyancy and nocturnal sinking characteristic of diatom Navicula sp.,which is regulated by intercellular physiological changes. Therefore diatom couldincrease the probability of contacting with the substratum, which opinion updates thetraditional point of view saying diatoms are completely passively landed on thesubstratum. Furthermore, the range of surface forces between diatom and substratum iscalculated based on theory. Also, body forces such as buoyancy and gravity play muchmore significant role on diatom approach process when the distance between the celland substratum is large.According to the microscopic analysis on gliding diatom, an updated diatomlocomotion model is researched and built, suggesting F-actins stored in the intracellularcircular structure could stretch out of the frustule to get in touch with substratum, withEPS as special medium to obtain high adhesion force. The new model well explains thegliding phenomena that cannot be clearly explained by existing model proposed byEdgar. Also, diatom locomotion and adhesion process are respectively simulated by themulti-agent platform NetLogo. The results prove the existence of communicationsbetween gliding cells, which helps diatom to form the aggregated pattern of biofilm.According to the analysis on interface forces and light experiments, the influenceof external factors on diatom adhesion is studied. Statistical results show that the polarfactor of surface energy and adhesion quantity are significantly correlated. Also, it is proved that adhesion is highly related with hydrogen bond and steric force. Accordingto the systemic research of how light influencing diatom settlement, light couldsignificantly inhibit cell settlement because of the spatial competition between circularstructure and chloroplast enclosed in the frustules. Also, diatom endogenous rhythm aswell as light conditions could influence the settlement preference, with the latter onemore important. When the diatom is illuminated during nighttime, as light intensityincreases, diatom settlement first decreases then increases; and even very weak bottomlight generates an obvious inhibition on diatoms settlement.Based on the above research on diatom adhesion mechanism, a newly developedcompound coating with environmentally friendly and effective antifouling function isdesigned, based on silicone elastomer and colored phosphor powder. Laboratoryinvestigations verify the low adhesion quantity and low adhesion strength on thiscoating. Diatom settlement quantity on this coating is only28%than on the stainlesssteel. And the marine immersion test indicates that this new coating performs betterantifouling ability than one kind of domestic tin-free self-polishing antifouling coating,showing a good application prospect.