Vascular stents could suffer from repetitive motions due to pulsatile blood pressure and daily activities. Stent fatigue resistance has thus become a critical issue for stent design. In this paper, an intriguing stent design concept aimed at enhancing the fatigue life was investigated. The concept was to re-distribute stresses more uniformly by tapering the stent strut width. Finite element models were developed to evaluate the mechanical integrity and fatigue safety factor of the stent under various loading conditions. Simulation results show that the fatigue safety factor of this novel stent design increased by 4 times that of a conventional stent. Conceptual stent prototypes were cut by a pulsed-fiber laser, followed by a series of expansions and heat treatments to gradually shape the stent to its target size. A rotating bending fatigue tester was built for this study and stent fatigue tests were conducted for proof of concept. Experimental results show that this stent design concept successfully enhanced the fatigue life as designed. Its fatigue cycle number jumped to 6∼7 times that of a conventional stent, which agreed well with the trend predicted by FEA simulations. The findings of this paper provide an excellent guide to greatly improve stent fatigue life.

Peripheral stent could fracture from cyclic loadings as a result of our blood pressures or daily activities. Fatigue performance has therefore become a key issue for peripheral stent design. A simple yet powerful tapered-strut design concept for fatigue life enhancement was investigated. This concept is to move the stress concentration away from the crown and re-distribute the stresses along the strut by narrowing the strut geometry. Finite element analysis was performed to evaluate the stent fatigue performance under various conditions consistent with the current clinical practice. Thirty stent prototypes were manufactured in-house by laser with a series of post-laser treatments, followed by the validation of bench fatigue tests for proof of concept. FEA simulation results show that the fatigue safety factor of the 40% tapered-strut design increased by 4.2 times that of a standard counterpart, which was validated by bench tests with 6.6-times and 5.9-times fatigue enhancement at room temperature and body temperature, respectively. Bench fatigue test results agreed very well with the increasing trend predicted by FEA simulation. The effects of the tapered-strut design were significant and could be considered as an option for fatigue optimization of future stent designs.