Preparation Of Micro-nano Structures On The Surface Of Medical Titanium And Characterization Of Performance

Titanium is the most widely used orthopedic implant material due to its good biocompatibility and mechanical properties.For example,as artificial hip joint,knee joint,it has received the wonderful clinical effect.But titanium is bioinert,after implanation in the body,it just lock with surrounding tissues mechanically,and can not make a strong chemical bonding with the bone;and in the physiological environment,the implant surface will be corroded and release metal ions and abrasive particles,which will cause inflammation and sometimes result in implant failure;in addition,the mechanical properties of titanium is also different from the natural bone,the high Young?s modulus of titanium implies that implants avoid the transfer of an entire applied load to the bone,which would generate a stress-shielding phenomenon and lead to the bone resorption.Based on the above problems,this work employed acid etching and anodic oxidation methods to build the micro-nano structure on the surface of titanium to improve the mechanical and biological properties of titanium surface,as well as the corrosion resistance.The friction and wear experiment,nano indentation test,polarization curve test and cell culture experiment were used to systematically evaluate the mechanical properties,corrosion resistance and biological properties of the titanium surface before and after surface treatment.The research results are listed as follows:?1?Micron structure is prepared on titanium surface via acid etching by controlling the etching time,temperature and acid concentration;Nanostructures with different sizes are prepared on Titanium surface using anodic oxidation through different electrolytes?NaF/water solution,NH₄F/glycol solution?,oxidation voltage and oxidation time.Combining the methods of acid etching and anodic oxidation,uniform and well-distributed micro-nano-structure was successfully prepared on titanium surface.?2?Friction and wear experiments show that,the friction resistance of titanium surface is much improved by the micro-nano-structure,nanostructure and microstructure followed,and the smooth titanium surface has the worst friction resistance;nano indentation experiments show that titanium surfaces with micro-nano structure and nano structure have elastic modulus close to human bone tissue,while,the titanium surface with micron-or smooth structure show higher elastic modulus;polarization curves confirmed that,titanium surface with micro-nano structure has better corrosion resistance than those with nano-or micro-structures,as well as the titanium with smooth surface.The improved mechanical properties and corrosion resistance of titanium are related to the surface structure and the thickening of the surface oxide layer.?3?The simulated body fluid soaking test showed that,titanium surfaces with micro-nano-structure and nanostructure could induce the formation of hydroxyapatite on the surface,but smooth surface and micro-structured titanium can not,confirming that the micro-nano-structure and nanostructure can significantly improve the bioactivity of titanium surface;in vitro cell culture experiments show that,titanium surface with micro-nano-structure is more conducive to cell spreading,proliferation and the expression of osteogenic genes,showing improved biocompatibility.The improved biological properties are related to the enhanced surface hydrophilicity,as well as the the surface structure and mechanical properties which are more similar with the natural bone tissues.