Functional and Structural Analysis of Auxetic Metamaterial Stent Designs for Thoracic Aortic Aneurysms Using Finite...

Thoracic aortic aneurysms often require large-diameter stent grafts; however, conventional designs exhibit poor wall apposition and limited adaptability to complex anatomies. Although auxetic metamaterials with a negative Poisson's ratio show promise for stent applications, the optimal design configuration remains unclear. Therefore, this study aimed to compare the mechanical performance of different auxetic stent designs and identify the most suitable configuration. Quasi-static experimental tests were conducted for validation, alongside finite element (FE) simulations under clinically relevant loading conditions, including parallel compression, radial compression, and radial expansion, to evaluate deployment behavior. Four auxetic designs, including rotating square (RS), re-entrant (RE), peanut (PN), and rotating triangle (RT), were investigated using magnesium alloy specimens. The results show that auxetic geometry significantly affects recoiling, stiffness, and deformation. The RT design demonstrated a more balanced mechanical response under the current evaluation criteria, with substantially lower radial stiffness (6291 N/m), representing an 84%-97% reduction compared to the other designs, and moderate foreshortening (7.10%), lower than RE (13.62%) and PN (9.61%) while comparable to RS (5.49%). Despite exhibiting a relatively higher recoil, these findings suggest its potential for controlled deployment and stable apposition.