Fabrication Of Micro-and Nano-Structure On Titanium Alloy Surface For Medical Implant By Laser Interference And Its Antibacterial Properties

Titanium alloys are widely used in the field of human implants due to their excellent heat resistance,strength and biocompatibility.In clinic,it is found that the surface of untreated titanium alloy has weak osseointegration and lacks effective anti infection ability.Therefore,in this paper,the periodic micro nano structure was fabricated on the surface of silver plated titanium alloy by laser interference induction.Silver and titanium alloy were fused to obtain the modified titanium alloy with good antibacterial propertiesIn this thesis,nanosecond laser lithography was used to change the surface morphology of titanium alloy by changing the laser parameters,different microstructure surfaces were formed on the surface of titanium alloy.Combined with ion sputtering coating technology,antibacterial layer was formed on the surface of titanium alloy.The main research contents are as follows:1.The construction of periodic structure of direct writing by nanosecond laser interference.The periodic micro nano grooves on the surface of Ti6Al4V alloy and silver plated Ti6Al4V alloy were fabricated by laser interference direct writing.The effects of laser energy density and silver film thickness on the structure and surface properties were studied.The results of X-ray photoelectron spectroscopy showed that there was obvious thermal effect in the process of interaction between laser and Ti6Al4V.SEM results showed that the micro groove structure was ideal under the condition of 150 m J/cm² laser energy density and 20 seconds processing time.The tribometer evaluation results showed that the periodic micro nano grooves on Ti6Al4V surface reduced the friction coefficient by 28.8%,and silver doping could further reduced the friction coefficient of Ti6Al4V surface.Moreover,the friction coefficient of Ti6Al4V surface could be further reduced by silver doping.The friction coefficient decreased with the increased of silver film thickness on titanium alloy surface.When the silver film thickness was 500 nm,the friction coefficient decreased by 60%.2.Study on the antibacterial properties of the surface micro nano structure of Ti6Al4V alloy.The surface antibacterial properties of Ti6Al4V alloy with micro nano grooves were studied after different thickness of silver film was deposited.A series of experiments were carried out on the control group,Ag_0nm,Ag_50nm,Ag_100nm,Ag_200nm,Ag_300nm,Ag_400nm and Ag_500nm.The results showed that the thickness of silver film had a significant effect on the anti S.aureus performance of micro nano groove structure on Ti6Al4V surface,and it increased with the increased of silver film thickness.The antibacterial rates of Ag_100nm,Ag_300nm and Ag_500nm were 91%,94.8%and 99.8%respectively.3.Biocompatibility analysis of micro nano structured Ti6Al4V surface.The released of Ag⁺in 0.9%Na Cl from the micro nano structure titanium alloy sample was measured.It was found that the release of Ag⁺from the sample at 500 nm was647.7 ppb,slightly higher than the normal standard.MTT assay was used to test the growth of L929 fibroblasts on the samples.The results showed that Ag_50nm?Ag_100nm?Ag_200nm?Ag_300nm had no cytotoxicity,Ag_400nm had slight cytotoxicity,and Ag_500nm had the strongest cytotoxicity.The most suitable Ag doped group for human implantation was Ag_300nm,with the antibacterial rate of 94.8%.4.Biocompatibility of micro nano structured Ti6Al4V surface.Ion release concentration and cell biocompatibility of samples with different film thickness were studied.The results showed that the Ag⁺released of the micro nano structured samples on the surface of Ti6Al4V alloy increased linearly with time in 0.9%Na Cl.The Ag⁺release was proportional to the thickness of silver film in the same release time.The MTT test of L929 fibroblasts in the samples showed that the samples of Ag_50nm,Ag_100nm,Ag_200nm and Ag_300nm showed no cytotoxicity,while the samples of Ag_400nmand Ag_500nm showed slight and strong cytotoxic respectively.In conclusion,the surface micro groove structure samples(Ag_100-300nm)of Ti6Al4V alloy surface have excellent antibacterial and biocompatibility in the range of 100-300nm,laser energy density of 150m J/cm² and time of 20 seconds.The antibacterial rate was more than 91%and the cell survival rate was more than 90%.It provides an experimental basis for reducing the risk of postoperative infection of biomedical implant material Ti6Al4V alloy.