Nonlinear radial force attenuation and stress-corrosion-crack induced fracture of biodegradable Zn alloy stents under vascular bioreactor conditions.

Zinc alloy vascular stents have emerged as promising candidates in the development of biodegradable stents in recent years. However, due to the complexity of the in vivo environment and the high cost of animal experiments, robust experimental evidence regarding stent degradation-induced radial support loss and the underlying failure mechanisms remains lacking. In this study, a bioreactor system capable of simulating both physiological chemical conditions and pulsatile hemodynamics was developed to investigate the degradation behavior and mechanical evolution of Zn alloy stents. The results revealed a pronounced nonlinear relationship between radial force attenuation and mass loss. Specifically, the radial force decreased by more than 50% when the mass loss was only approximately 25%, demonstrating a distinct "cliff-like" failure pattern. This rapid deterioration was mainly attributed to stress corrosion cracking (SCC) occurring in the V-shaped load-bearing regions of the stent. During expansion, severe stress concentration and high plastic strain developed in these regions, which, combined with micro-galvanic corrosion, promoted crack initiation and propagation. These experimental findings verify that the mechanical failure of Zn alloy stents is dominated by local structural vulnerability rather than uniform degradation, suggesting that geometric optimization of critical regions is more effective than overall material enhancement for improving long-term structural reliability. STATEMENT OF SIGNIFICANCE: This research has revealed a pronounced non-linear relationship between radial force attenuation and mass loss in biodegradable Zn alloy vascular stents via a customized bioreactor system. The stents exhibited a distinct "cliff-like" failure pattern, which is primarily dominated by stress corrosion cracking (SCC) localized within the V-shaped load-bearing regions of the stent. This finding indicates that geometric optimization of critical high-stress regions is far more effective for ensuring long-term structural reliability than overall material alloying alignment.