Effect Of Ion Implantation And Vacuum Annealing On Structure And Anticoagulant Properties Of Titanium Oxide Films

The antithrombogenicity remains a primary problem for the biomaterials used in blood-contacting medical devices and artificial organ, the improvement of anticoagulation is therefore critical for the development and application of these biomaterials. There is a close relationship between the hemocompatibility of inorganic materials surface and the structure and properties, especially the surface characteristics, of materials. In this light, it is necessary to investigate the causal relationship between materials surface characteristics and antithrombogenicity, understand the interactions occur in the interface between blood and materials, reveal the mechanism of enhancing antithrombogenicity by surface modification, and explore the technics and methods of material processing. The results of above studies are of theoretical significance and practical value in the design of biomaterials and medical device with good hemocompatibility.In this work, titanium oxide films with diverse structures and properties were fabricated by unbalanced magnetron sputtering, and then utilize ion implantation and vacuum annealing to modify the film.The surface topography and roughness of the films were analyzed by Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM). The structure and composition of the film were characterized by X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS) and its valence band spectroscopy (VXPS), Fourier Transform Infrared Spectroscopy (FTIR). Four-point probe resistance meter and contact angle apparatus were employed to measure the electroconductibility and surface energy respectively. In vitro test is used to evaluate the hemocompatibility of Ti-O film.Through the analysis of the effect of ion implantation and vacuum annealing on structure, property and antithrombogenicity of Ti-O film, to a certain extent, some causal relationships between structure and property have been established. The main conclusions of this dissertation were as follows:1. The effect of ion implantation and vacuum annealing on structure and property of Ti-O film(1) After treated by vacuum annealing, the color of monocrystal TiO2and Ti-O film turn from approximate colorless to mazarine, the conductivity of film improved, on the surface of film exist Ti3+, hydroxy content, hydrophilia and the polar fraction of surface free energy all increased. The generation of thermally induced oxygen vacancy and low-valent titanium lead to three results:â‘ The energy band structure of the film have been changed, and the square resistance reduced.â‘¡The specific absorption of light wave cause the Ti-O film shows mazarine.â‘¢When H2O contact with oxygen vacancies, the H2O decomposed to form-OH. Consequently, hydroxy content, hydrophilia and the polar fraction of surface free energy all increased.(2) Treated by vacuum annealing, and after a period time, the remarkable hydrophilia of Ti-O film disappear, the hydroxy content on the surface decreased. The complex reactions, which ambience substance take part in and include dissociation and adsorption, take place on the surface of Ti-O film lead to the disappearance of oxygen vacancies, and the hydroxyls were replaced or blanketed, hydrophilia reduced finally.(3) Ion implantation cause the damage of crystal structure, this has further led to an improvement in conductivity of film. Vacuum annealing can repair the damage of crystal lattice, and this result in further reduction of film square resistance. The hydrophilia and surface adsorption states of film modified by ion implantation were mediated by effect of the ion implantation and vacuum annealing collectively and present diversity.2. The relationship between hemocompatibility and the structure and property of Ti-O film(1) Surface hydroxylation caused by vacuum annealing improves the antithrombogenicity of Ti-O film obviously.â‘ With the increase of the surface hydroxy content, hydrophilia and the polar fraction of surface free energy of film surface improved. The Ti-O film with abundant hydroxyl, excellent hydrophilia and high ratio of polar to disperse component of surface free energy could be beneficial to reduce the adsorption of fibrinogen, keep it normal conformation and minimize the platelet adhesion on the surface, so improve the antithrombogenicity of the film.â‘¡Oxygen vacancy and low-valent titanium lead to the surface hydroxylation of film and form the energy band structure with n-type semiconductor feature simultaneously, and this structure restrains the degeneration of fibrinogen, thus the antithrombogenicity of the film been improved.â‘¢Oxygen Vacancy were be healed, the hydroxylation were be replacement or concealment by other adsorbate, the hydrophilic of the surface decrease, and the ratio of polar component to disperse component of surface free energy decrease, the advantage antithrombogenicity caused by vacuum annealing attenuated gradually.(2) If the percentage of adsorption oxygen more than50%after ion implation, the antithrombogenicity would be decrase; furthermore, the blood compatibility of the film will be improve if the percentage of adsorption oxygen less than50%after vacuum annealing treatment.