The effect of fs-laser micromachining parameters on surface roughness, bio-corrosion and biocompatibility of nitinol

Abstract

The thermo-pseudo elastic property of nitinol attracts the manufacturing sector to produce more biomedical implants from this binary alloy. However the release of Ni ions from the implanted nitinol causes a toxic nature and poses a harmful effect if the implants are in a physiological environment for a long period. This research is an attempt to control the release of Ni ions with improved bio-corrosion resistance and biocompatibility by mitigating the process parameters of femtosecond laser micromachining. The exclusive nitinol specimens are synthesized through the blending-compaction-sintering route. The specimens are machined under three varied levels of laser parameters to the dimensions compatible with the common cardiovascular stent. The surface roughness examination confirms the very minimal surface roughness of 10.83 nm is achieved from level 2 machining condition (36 W laser power, 500 mm/s scanning speed, 9 kHz pulse frequency). The potentiodynamic polarization technique is followed in the presence of a Simulated Body Fluid (SBF) environment to assess the bio-corrosion behaviour. XRD and SEM investigating methods are employed post-corrosion test, to assess the deposition of the TiO2 layer. The minimal bio-corrosion rate is observed from the specimen with very minimal surface roughness. XRD and SEM results explore the thicker deposition of the TiO2 layer for the specimens from level 2 machining conditions, with minimal corrosion rate and surface roughness.