Preparation And Properties Of Microstructured And Layer-by-layer-assembled Antifouling Surface Of Bionic Laminaria Japonica

Marine biofouling is an important obstacle to the development of marine cause.Problems such as huge economic losses caused by biofouling and environmental damage caused by toxic antifouling agents have not been resolved.Therefore,it is of great significance to develop a novel,environmentally friendly antifouling materials.This paper was inspired by the excellent antifouling performance of the Laminaria japonica,and probes into the factors that it has antifouling performance,and makes bionic microstructured and layer-by-layer-assembled antfouling coating materials based on bionic method.The microstructure of the material surface was characterized by SEM,AFM,TEM.The chemical composition,charge and wettability of the material surface were studied by ATR-FTIR,XPS,Zeta and contact angle tester.Meanwhile,the antifouling properties of the materials were discussed by anti-seaweed adhesion and bacteriostatic test.The factors that make Laminaria japonica have antifouling performance were explored.The surface morphology,elastic modulus,chemical composition,surface energy,Zeta potential and surface secretion were analyzed.Under dry and humid conditions,the surface of the middle and edge parts of it has anisotropy and isotropic structure,and the elastic modulus is 2.3 MPa,0.98 MPa,2.4 MPa,which shows good flexibility and low elastic modulus,respectively.The surface energy of Laminaria japonica was 30～40 mN/m,which was close to the surface energy range when the adhesion force of fouling organisms was minimized.Isotropic and anisotropy structured PDMS and EP surfaces were prepared by template method.The effects of surface morphology and elastic modulus on the inhibition of biological fouling adhesion were investigated.By comparing the elastic modulus of PDMS and EP with smooth,isotropic and anisotropic,the change of the micro-morphology can influence the change of the elastic modulus,and the elastic modulus can be reduced after the surface was structured.The adhesive force ranges of smooth PDMS and EP surfaces were 0～40.2 nN and0～8.8 nN,respectively,indicating that the elastic modulus would affect the adhesion ability of seaweed.Higher elastic modulus EP surface adheres more seaweed than low elastic modulus PDMS surface,while structured PDMS and EP surface can reduce the attachment of seaweed,and the adhesion amount of the Phaeodactylum tricornutum,Nitzschia closterium and Navicula exigua on the surface of the isotropic structured PDMS were the lowest,22±2.5diatoms mm^-2,452±26 diatoms mm^-2and 381±35 diatoms mm^-2,respectively.The polyelectrolyte layer was formed on the isotropic structured PDMS surface by layer-by-layer assembly method,and the effects of micromorphology and chemical modification on the antifouling performance were studied.The results showed that,when n=5,（GHPEI/ALG）*5 polyelectrolyte layer was deposited on the surface without changing the surface micro-morphology.At this time,the water contact angle of the PDMS surface decreased from 117.5°to 35.3°,and the isoelectric point was increased from 4.12 to 6.12.It was described that the polyelectrolyte layer not only improves the hydrophilicity of the surface,but also can effectively adjust the surface charge.Through the anti-seaweed adhesion test and antibacterial test of（GHPEI/ALG）*5 polyelectrolyte layer,it was found that the seaweed adhesion on the smooth and structured PDMS surface modified by（GHPEI/ALG）*5polyelectrolyte layer were 14±6 diatoms mm^-2and 9±5 diatoms mm^-2,respectively,and the antibacterial rates were 92.4±1.7%and 96.2±1.3%,respectively,indicating that the structured PDMS surface modified by（GHPEI/ALG）*5 polyelectrolyte layer had better antifouling performance.The chemical modification and microstructure of the surface have certain synergistic effect on the antifouling performance.Chitosan nanocapsules containing capsaicin（CAP@CS）were prepared by microemulsion method,and pH response（GHPEI/ALG-CAP@CS-x）*n polyelectrolyte layers were formed on isotropic structured PDMS surface by layer-by-layer assembly method.The results showed that when the chitosan concentration was 0.5 mg/mL and dialyzed in PBS solution of pH=8.5,the particle size of CAP@CS nanocapsules was about 200 nm.The polyelectrolyte layer containing CAP@CS nanocapsules was uniformly deposited on the surface without changing the micromorphology of the surface when n=10 and ALG:CAP@CS=8:2.Hence,the water contact angle of the surface was 17.6°and the isoelectric point was 8.77.The anti-algae adhesion test and antibacterial test show that（GHPEI/ALG-CAP@CS-8）*10 has more long-acting antifouling performance,and its diatom adhesion was 23±4 diatoms mm^-2,and the bacteriostatic rate was 99.2±0.6%.