The Effect of Platinum Core Ratio on the Mechanical, Thermal, and Fatigue Performance of Superelastic Nitinol Drawn Filled Tube (DFT®) Used in Medical Devices

Niti-DFT®-Platinum composite wires combine the beneficial properties of two materials (Nitinol and platinum) into one wire product. The outer sheath of Nitinol provides the wire with superior superelasticity and fatigue strength while the dense platinum core provides the radiopacity needed for viewing under X-Ray. In this study, composite wires with varying platinum core area ratios are evaluated to determine the effect of the platinum fill on the mechanical and thermal properties of the overall Nitinol composite wire. This paper serves as an extension of the work done by J.E. Schaffer and R. Gordon titled “Engineering Characteristics of Drawn Filled Nitinol Tube”. The relationship between core area ratio and the properties critical to the performance of implanted Nitinol medical devices (namely Active A_f, plateau stresses, tensile strength, and elongation to failure) is explored. Rotating bending fatigue performance and corresponding fracture analysis is also characterized. This study assists the medical device engineer in balancing the benefits of achieving superior radiopacity under X-ray fluoroscopy with the effects on the critical properties controlling medical device performance.