Suppression of nickel out-diffusion from porous nickel-titanium shape memory alloy by plasma immersion ion implantation

Abstract

Summary form only given. Porous nickel titanium is a promising material for medical application not only because of its super elasticity and shape memory effect but also the porous structure which may enhance bone growth due to the increased surface area. It is thus especially suitable for bone tissue in-growth and fixation of biomedical implants. However, like its dense counterpart, Ni leaching from the materials causes health concern. Thus, in order to suppress Ni diffusion from the materials to body fluids and tissues in humans, a diffusion barrier or similar structure must be introduced. In this work, we produced this diffusion barrier layer by oxygen or nitrogen plasma immersion ion implantation (PIII). In vitro tests were conducted by immersing the plasma-treated NiTi into simulated body fluid (SBF) at 37plusmn0.5degC for 5 weeks and the resulting SBF was analyzed for Ni and Ti using inductively-coupled plasma mass spectrometry (ICMPS). Our results show that Ni leaching is significantly mitigated by both nitrogen and oxygen PIII.