Design And Manufacture Of Micro-nano-structured Titanium Alloy Surface And Its Bioactivity

The biomedical titanium alloys are widely used in medical implants owning to its good physical and mechanical properties. However, titanium alloys are surface bio-inert, which results in poor osseointegration. Therefore, it is the key issue problem to improve the combination capacity between implants and human tissue. The micro topography of titanium alloy surface affects the combination of implant and tissue. This paper studied the design and manufacture of micro-nano-structured titanium alloy surface and its bioactivity.The scales of micro-nano-structures on implant surface were studied based on the bionics theory. The natural bone surface characteristics were observed and characterized. It was found that the surface of natural bone had micro-pits of 50～200μm in diameter,30～150μm in depth and microgrooves of 10～100μm in width. The inorganic particle size of bone was nanoscale. Therefore, the designed micro-pits were 100um in diameter and 300μm in interval and the scale of nano-structures was from 1nm to 100nm.The method of creating micro-pits on titanium alloy surface was proposed. The parameters that influence the laser processing were analyzed. The relationship between the Q frequency or current and the morphology or depth of micro-pits was studied by laser experiments. The optimized current was 13A and Q frequency was 3 KHz.The method of creating nano-structures by multiple acid etching was presented. The research showed that acid etching could not only removed the clinkers produced by laser processing, but also created nano-structures on the micro-pits array. The sample surfaces were observed and analyzed by digital microscope, scanning electron microscope (SEM) and energy dispersive spectrometer (EDS).The bioactivity of micro-nano-structured titanium alloy surface was investigated. The bioactivity of different kinds of surfaces were evaluated by simulated body fluid (SBF) test and cell culture test. The results showed that the micro-nano-structured surfaces created by laser processing and acid etching were most conductive to cell adhesion, proliferation and cell spreading. A large number of filopodium on the cell made the cell firmly attach to the material. The results showed that the surfaces with micro-nano-structures had higher biological activity.