A Method To Locally Tune Pseudoelasticity Of NiTi Stent

The shape memory effect (SME) and excellent biocompatibility of Nitinol have made it the material of choice for stent applications. Conventional fabrication processes for NiTi stents limit their performance since only a constant pseudoelastic (PE) force and geometry can be achieved along the length. However biological systems rarely have constant forces (i.e. radial) or geometries, hence variable PE force would allow the design and fabrication of a more compatible device. The current work implements a novel method, known as the multiple memory material (MMM) technology, to locally modify the pseudoelasticity of nitinol-based stents to enable conformity to the surrounding biological system. This was achieved through the application of a high power density laser that locally modifies the microstructure and composition for predetermined locations along the tube. Subsequently, the tube was cut into tensile coupons that exhibited altered PE properties as compared to the original base material. Finally, a complete stent was fabricated and evaluated both thermally and mechanically to demonstrate the localized control and customization of its thermomechanical properties.