Flow Mechanism And Hydrophilic And Antibacterial Performance Study Of Surface Modification For Titanium Implants

Titanium(Ti)has been widely used in the field of dental implants.However,clinical problems of implant shedding and bacterial infection still exist.To solve the clinical problems,enhancing the hydrophilic and antibacterial properties of Ti implants via surface modifications is an effective approach.Regarding to the hydrophilic modification,the microstructure prepared by a sand-blasting large grit acid-etching(SLA)process can enhance the inherent hydrophilicity of Ti surface.However,existing research has focused on experimental studies without a specific characterization of the two-stage microstructure and a flow and wetting model oriented to the hydrophilic modification by microstructure,making it difficult to explore the flow mechanism of a hydrophilic surface and conduct the optimization study.Regarding to the antibacterial modification,silver nanoparticles(AgNPs)can be used as antibacterial coatings due to their extensive and excellent antibacterial activity.To avoid the potential toxicity from high concentrations of silver,the thickness of the coating should be precisely controlled at the nanoscale,which is expected to be solved via the electron-beam evaporation(EBE)process.However,the effect of the antibacterial film on the hydrophilic modification and the effectiveness of the EBE process in the antibacterial field remain to be investigated.In view of the above problems,following researches have been conducted in this dissertation:Based on a Shan-Chen(SC)multi-component multi-phase lattice Boltzmann method(LBM),a flow and wetting model of droplets on solid surfaces was established.A contact angle predicting algorithm controlled by the three-phase interface was introduced.To accurately simulate the contact angle,key parameters of the model were discussed.A simulation example and corresponding experimental results show that the average error of the model is less than 7%,which indicates that the model can be used to accurately simulate the dynamic process and predict the contact angle.The proposed model provided theoretical guidance and an effective method for exploring the hydrophilic mechanism and conducting the optimization study of the two-stage microstructure Ti surface.Regarding to the SLA process,the decoupling and characterization of the two-stage microstructure were constructed.Based on the flow and wetting model,the hydrophilic mechanism of the two-stage microstructure and a stepwise optimization scheme for the surface design were proposed.The hydrophilicity of the primary microstructure increases with the increase of the liquid-solid interface area,and the secondary microstructure further enhances the hydrophilicity by decreasing the capillary effect and increasing the liquid-solid interface.The response surface method(RSM)was used to optimize the characteristic parameters of the two-stage microstructure.Optimal and experimental results show that the contact angle was decreased from 43.95° to 16.88°,indicating the successful hydrophilic modification of the Ti implant.The corresponding relationship between process parameters and film thickness was established via the EBE process and a calibration method of film thickness,and the precise preparation of a nanoscale AgNPs film was realized.In addition,the effect of the antibacterial film on the hydrophilic modification was investigated.An excessive thickness of the film will break the two-stage microstructure and cause the decrease of hydrophilicity.However,the 3 nm and 15 nm films have little effect on the hydrophilic modification,which can realize the antibacterial surface modification of the Ti implant.A surface modification strategy was proposed for preparing a composite Ti surface with excellent hydrophilic and antibacterial properties.A series of biological bacteria experiments were conducted to evaluate the antibacterial properties of the samples,verifying the effectiveness of the EBE process in the antibacterial field.Experimental results show that the 15 nm AgNPs film exhibits an excellent antibacterial property,and the antibacterial rates(AR)against Escherichia coli(E.coli)and Staphylococcus aureus(S.aureus)were 96.34% and 97.86% respectively.In addition,the effect of the antibacterial film on the hydrophilic modification was investigated.Results show that the 15 nm film has little effect on the hydrophilic modification with an excellent hydrophilicity.Therefore,by adding a 15 nm AgNPs film on the Ti surface with the two-stage titanium microstructure,the hydrophilic and antibacterial properties were both enhanced.