Three-dimensional Morphological Evaluation And Antifouling Characteristic Analysis Of Shell Surfaces

The marine fouling organisms which affect the marine transport seriously not only expend more fuel but also enhance the hull erosion so as to decrease the ship economy and safety.The classical antifouling methods are using toxic coatings,which will gradually be forbidden because of the bad impact on marine environment.Therefore developing new kinds of environmentally friendly antifouling methods is the trend in the marine antifouling field.People developed the micro-structural antifouling method by biomimetics biologically inspired from marine surfaces that remain clean in the sea.Shell moves very slow in the sea without fouling organisms on the surface,which is similar to the situation that ships are adhered by fouling creatures mostly when they are static in the harbors.Hence,the micro-topography of antifouling shell surface has a great significance to the ships for being away from fouling.However,the gradually changed microstructure of shell surface makes the characterization of three-dimensional morphology harder and hinders the development of microstructural antifouling surface.This study develops a new three-dimensional characterization system of shell surface and analyzed the correlation between surface morphologies and antifouling properties by measuring shell surfaces.Three kinds of shell species Mimachlamys nobilis,Scapharca broughtonii and Dosinia japonica were selected as bionic objects in this study.Based on the present documents and the collected numbers of shell samples,fouling organisms exist on the surfaces of S.capharca.On the contrast,the surfaces of D.japonica are clean.However,clean area and fouling area both appear on the surface of M.nobilis.Considering the profiles of the three types of shell morphology,9 parameters were defined to describe the surface characterizations:W_p?the profile width between the adjacent peaks?,W_v?the profile width between the adjacent valleys?,H?the profile valley depth?,R_p?the profile peak radian?,R_v?the profile valley radian?,R_sk?the ratio of profile height to width which are between peak and its adjacent valley?,R_pvp?the ratio of profile widths which are between valley and its adjacent peaks?,R_vpv?the ratio of profile widths which are between peak and its adjacent valleys?and R_prh?the ratio of profile heights which are between peak and its adjacent valleys?.The Digital Stereomicroscope was used to get the three-dimensional features of shell surfaces.Then the profile curves were obtained to get the curve equations by cftool in MATLAB.A small program was written to calculate the 9 characteristic parameters.At last,several commonly used digital features and one-way anova analysis were both utilized to compare three different kinds of shell surfaces and different antifouling properties of M.nobilis.The results show that shell species have a significant influence on the 9 defined parameters by making species as the control variable.On the other hand,the comparison between clean and fouling morphologies of M.nobilis surfaces suggest that W_p,W_v,H,R_p and R_v also have a great difference and there are no difference in R_sk,R_pvp,R_vpv and R_prh.The one-way anova analyses also prove the effectiveness of three-dimensional characterization system of shell surface.The comprehensive results and statistical regularities of antifouling morphologies are given by correlating the surface structures with the antifouling properties.Obviously,the values of W_p,W_v and H of antifouling topographies are much less than that of fouling topographies.However,the values of R_p and R_v are also significantly different between antifouling topographies and fouling topographies,but the conclusions are opposite in two different analysis.For R_sk and R_vpv,the values of D.japonica are less than that of M.nobilis and S.capharca in different species'analysis,but no obvious difference in single species'analysis.For the last two parameters R_pvp and R_prh,the values of S.capharca are greater than that of M.nobilis and D.japonica in different species'analysis,but no apparent difference in single species'analysis.