COMSOL模拟的钛合金基体表面纯镁涂层制备及性能研究

Preparation and Properties of Pure Magnesium Coating on Titanium Alloy Simulated by COMSOL

目的解决目前临床应用的钛合金植入物功能性欠佳的问题,既利用钛合金的力学性能优势,又发挥镁基金属的生物活性作用,把镁基金属的应用拓展到承力部位,为理想骨植入材料提供一种新的选择。方法采用真空蒸镀技术在钛合金表面制备镁涂层,采用模拟软件结合实验的方法,利用COMSOL Multiphysic软件模拟真空蒸镀法在钛合金基体上制备纯镁涂层,结合涂层沉积实验,研究不同蒸发温度、沉积时间和基体表面温度对镁涂层质量的影响,利用模拟结果设计实验,并进行优化,对涂层的表面形貌、浸润性、可降解性、抗菌性进行实验分析。结果在钛合金基体表面制备的纯镁涂层靠近蒸发材料中心轴的表面部分沉积的涂层较厚,涂层厚度由中心轴向四周逐渐减小,最厚部位比最薄部位厚约13.6%;在影响涂层厚度的3个因素中,材料蒸发温度的影响最大;在700℃下制备的涂层的表面颗粒分布均匀,涂层表面平整度最高,且其接触角大于90°,表现为疏水性,在该温度下体外降解速率最低,材料抗菌率>90%。结论采用真空蒸镀技术可在钛合金基体表面获得纯镁涂层,该涂层提高了钛合金基材的生物活性,其降解产生的碱性环境具有抗菌性,对大肠杆菌和金黄色葡萄球菌具有较强的杀灭作用,有望提高植入材料的稳定性,解决术后感染问题。

Because of the excellent mechanical properties and biocompatibility,titanium(Ti)alloy has been widely used as orthopedic implants in clinical.However,as a bioinert material,aseptic loosening of Ti alloy implants always takes place after surgery due to the lack of osseointegration ability,and infection caused by bacteria is always unavoidable.Therefore,the bioactivity of Ti alloy needs to be further improved.Magnesium(Mg)-based metal is biodegradable.The alkaline environment generated through degradation process and the metal ions such as Mg2+release have multiple biological activities which is beneficial to bone tissue reconstruction,such as antibacterial properties,osseointegration and vascularization.Nevertheless,the strength of Mg is relatively low,and it cannot be applied to load bearing position of human body.Therefore,the work aims to fabricate Mg coating on Ti alloy and combine the advantage of mechanical properties for Ti alloy and biological activity for Mg coating,providing a potential alternative choice for bone implant materials.COMSOL Multiphysic software was adopted to simulate the fabrication of pure Mg coating on Ti alloy by vacuum evaporation method.Combined with practical coating deposition experiments,the effect of evaporation temperature,deposition time and substrate temperature on the quality of Mg coating was investigated.The coating deposition parameters were optimized base on the simulation results.The surface morphology,wettability,degradability and antibacterial properties of the coating were studied.The simulation results showed that the pure Mg coating prepared on the surface of Ti alloy substrate was thicker near the central axis of the evaporation material.The thickness of coating gradually decreased from the central axis to periphery,and the thickest part was 13.6%thicker than the thinnest part.The thickness of the pure magnesium coating was proportional to the deposition time,and deposition rate was about 0.000229 mm/min.Among the three factors that affected the thickness of coating,the evaporation temperature had the greatest effect.As the evaporation temperature gradually increased,the gaps between particles gradually decreased,and the particle size gradually became larger and there was a tendency to merge together.For all evaporation temperatures,the contact angles of the coating were all greater than 90°,showing hydrophobicity,which was helpful to reduce the risk of bacterial contamination and postoperative infection for biomedical metal materials.Therefore,the coating possessed good antibacterial,self-cleaning and anticoagulation functions.The in vitro degradation experimental results showed that the coated samples prepared under 700℃could maintain an alkaline environment and Mg coating sustained for a certain period of time which was enough for antibacterial behavior.The antibacterial rate for E.coli and S.aureus reached more than 90%,showing good antibacterial properties and the coating could effectively resist the postoperative infection of implanted materials.The high pH degradation environment of Mg-coated samples had an inhibitory effect on E.coli and S.aureus,which was of great significance for bone implantation materials.Especially,in the early stage of implantation that was very important for inhibiting bacterial growth,the application of Mg as antibacterial agent would reduce the use of antibiotics and improve the success rate of surgery.The application of Mg coating will bring a new hope for the solution of the infection problem faced by orthopedic implant devices.