Mussel-Inspired Biomimetic Surface Functionalization And Metallization

The techniques to modify substrate surfaces are significant for many industrial and research applications. The toolbox of methods available so far covers a large number of approaches with their specific advantages and limitations. Among them, spontaneous self-assembly and organization of designed molecules and polymers incorporating adhesion and other functions, are particularly attractive as they constitute cost-effective, easy-to-unscale techniques, applicability to large areas and three-dimensional devices of complex shape, and conformity with micro and nano scale surface technologies, while requiring only minimal amounts of materials.Recently, inspired by and studied on the composition of adhesive proteins in mussels, the adhesive mechanisms and adhesive behaviors of polydopamine have been reported. The results indicate that dopamine (or 3,4-dihydroxy-phenylalanine) and other catechol compounds perform well as binding agents for coating various substrates, including organic, inorganic and metal materials. The oxidative polymerization of dopamine and the spontaneous deposition of polydopamine on various surfaces provide a powerful route for surface modification and functionalization. Secondary reactions with the polydopamine layer can be used to create a variety of ad-layers, including self-assembled monolayers, through the deposition of long-chain molecular building blocks, metal films by electroless metallization, and bioactive surface via grafting of macromolecules.In this work, suface modification of polyimide (PI) films and glass beads were carried out by utilizing dopamine self-polymerization and deposition. Electroless plating of silver on the as-prepared surfaces was performed to prepare conductive or antibacterial surfaces. The details of the work are as follows:(1) A novel method was developed for the preparation of reflective and electrically conductive surfacesilvered polyimide (PI) films. Polyimide films were functionalized with poly(dopamine), simply by dipping the PI films into aqueous dopamine solution and mildly stirring at room temperature. Electroless plating of silver was readily carried out on the poly(dopamine) deposited PI (PI-DOPA) surface. The surface compositions of the modified PI films were studied by X-ray photoelectron spectroscopy (XPS). XPS results show that the PI-DOPA surfaces were successfully deposited with ploy(dopamine) and were ready for electroless deposition of silver. The poly(dopamine) layer was used not only as the chemisorption sites for silver particles during the electroless plating of silver, but also as an adhesion promotion layer for the electrolessly deposited silver. The as-prepared silvered PI films show high conductivity and reflectivity, with a surface resistance of 1.5Ωand reflectivity of 95%, respectively.(2) Immobilization of silver nanoparticles on the dopamine functionalized polyimide (PI) films was carried out by photo-induced silver ion-reduction under atmosphere conditions. The dopamine was successfully deposited on the PI surface in mild aqueous environments. The effects of pH, dopamine concentration and reaction time on the dopamine polymerization were investigated. The water contact angles of the poly(dopamine) functionalized PI films reduced remarkably in comparison with that of the pristine PI film. The chemical composition and structure of the UV-induced deposited-silver on the modified PI films were characterized by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The topography of the modified PI films was investigated by scanning electron microscope (SEM). The deposited poly(dopamine) layer acted as binding sites for the silver ions. The silver-plated PI films showed good antibacterial activity due to that biofilm formation was inhibited on the polymeric surfaces in contact with bacteria.(3) A simple method was developed to prepare silver-coated silica beads which were functionalized by dopamine. Surface modification of prisitine glass beads was carried out by dopamine polymerization and deposition followed by electroless plating. The content of ammonical AgNO3 in deionized water was varied with respective amount of glucose solution in the seeding growth process and a uniform and relative dense coverage of silver nanoparticle seeds on the surface of silica beads was achieved. The chemical composition of the Ag/silica beads core-shell composite particles were studied by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). In addition, the morphologies of the composite particles were observed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDX). The poly(dopamine) layer was used as the chemi-sorption sites for silver particles and promoted the deposition of silver. The conductivity of as-prepared Ag/silver beads composite particles was tested by four-probe resistivity tester and the resistivity of the particles was 10 mQ.In conclusion, this paper shows that dopamine is a versatile method to functionalize the surface of substrate materials range from polymers to inorganics with various shapes, and the combination of the following electroless plating technique could prepare surface metalized composites with good adhesion between the metal with the substrate.