Theory and principles of nickel - titanium shape memory alloy as smart material on the design of cardiovascular stents

Abstract

The changes in manufacturing environment are characterized by aggressive competition on a global scale and rapid changes in process technology. The development of ‘smart’ materials and the need of systems that can be readily reconfigured for a wide range of requirements have become necessary for the future. Nickel – Titanium alloy is a ‘smart’ material with shape memory effect, dominated by a transition between the austenite phase and the martensite structure. The chemical composition and the heat treatment have a significant effect on the transformation temperature of the material; in order to take advantage of the properties of NiTi control of this temperature is essential. One of the applications of NiTi is stents, taking advantage of the NiTi biocompatibility, large recoverable deformation, good fatigue life, superelastic and shape memory properties around body temperature, allowing the development of self-expanding stents. This works has as purpose the development of a constitutive model of NiTi phase transformation from martensite to austenite and the effect of heat treatment on the setting of transformation temperature, to be applied in the design, numerical simulation and laser manufacture of self-expandable stents. Also, considering that the improvement of stents designs and operation by the use of smaller dimensions, functional materials or polymers requires research about modern surface coatings and stent laser manufacturing methods is required, this research also intends to establish the state of art about stents materials, surface coatings and manufacture.