The Regulation And Mechanism Of Anti-hydrophobic Functional Surface Anti-dopa Adhesion Characteristics

Adhesion of mussel foot proteins(Mefps)to a variety of surfaces has been widely concerned.A large amount of 3,4-dihydroxyphenylalanine(DOPA)in Mefps is considered to be a major chemical substance with strong wet adhesion,but the mechanisms behind the mussel adhesion at surfaces with different properties are far from being understood.Firstly,a series of self-assembled monolayers(SAMs)with different end-functional groups were prepared.The interaction between DOPA and SAMs was studied by chemical force microscopy(CFM).With the increase of hydrophobicity of SAM-OH surface to SAM-C6H5 surface,the adhesion gradually increased from 0.66 nN to 4.43nN,and as the surface hydrophobicity continued to increase,the adhesion decreased,indicating that hydrophobic interaction does not play a decisive role in the DOPA-surface adhesion process.By the use of classical and extended Derjaguin-Landau-Verwey-Overbeek(DLVO)theories,the contribution of non-DLVO forces was isolated.We found out DOPA can adhere to different surface functional groups,since o-hydroxy or aromatic ring in DOPA residues alone can control the adhesion process,with the orientation being perpendicular or parallel to the surface.Secondly,the nanostructured surfaces of the nasturtium leaf waxes with different crystal densities were prepared by organic vapor deposition on the silicon wafer with 50nm,100nm,200nm,and 500nm thickness.The adhesive properties of the nanostructures were tested by atomic force microscopy with colloidal probes which were modified with DOPA molecules.It was found that the surface of nanostructures with a thickness of 200nm had the lowest adhesive interaction with the probe.The surfaces of bionic shark skin with different heights of 1,3,5μm were prepared by reactive ion etching method.The surfaces of hierarchical structure were prepared by organic vapor deposition on the surface of bionic shark skin with a thickness of 200nm.It was found that the adhesion(0.97nN)of DOPA to 5μm height of the micro-nanocomposite surface was significantly smaller than that of the nanostructured surface(2.02nN)prepared by organic vapor deposition at 200nm thickness on the silicon wafer,and compared with the latter material,the former one not only has better anti-DOPA adhesion effect,but also has strong hydrophobic and excellent resistance to water adhesion,beingmimic the nasturtium leaf surface.