Optimizing mechanical properties of braided nitinol stents through geometric parameter engineering: Insights from experiments and finite element analysis

Abstract

Understanding the structure-property relationship of braided nitinol stents is critical for developing devices with optimized mechanical performance for endovascular applications. This study systematically investigates how key geometric parameters (including points per inch (PPI), braiding angle, wire count, wire coverage coefficient (WCC), diameter, and braiding architecture), influence the compressive, bending, and torsional behavior of nitinol stents. A combined experimental and finite element analysis (FEA) approach was used to evaluate 54 configurations under three mechanical loading conditions. Results reveal strong linear correlations (R² ≥ 0.90) between mechanical performance and PPI, WCC, braiding angle, and diameter. Wire count plays a contradictory role in mechanical performance: higher wire numbers increase bending and torsional stiffness but reduce radial strength. The 1-1 braid structure provides superior torsional and bending strength compared to the 1-2 structure, without compromising compressive strength. Notably, in small-diameter (1 mm) catheters, increasing PPI reduces flexibility and torsional stiffness, contrary to trends observed in larger diameters. These findings offer a comprehensive design guideline for tailoring stent architecture to match specific mechanical and clinical requirements.

Keywords

Nitinol stents / braided structures / mechanical performance / finite element analysis / structural optimization

References

[1] Reorowicz P, Tyfa Z, Obidowski D, Wiśniewski K, Stefańczyk L, Jóźwik K, et al. Blood flow through the fusiform aneurysm treated with the Flow Diverter stent-Numerical investigations. Biocybern Biomed Eng. 2022; 42(1): 375-390.

[2] Janiga G, Daróczy L, Berg P, Thévenin D, Skalej M, Beuing O . An automatic CFD-based flow diverter optimization principle for patient-specific intracranial aneurysms. J Biomech. 2015; 48(14): 3846-3852.

[3] Liu X, Tao H, Li C, Lin J, Guan G, Wang F, et al. Effect of NiTi parameters on the mechanical properties of integrated braided stents. Text Res J. 2023; 93(3-4): 701-712.

[4] Singh C, Wong CS, Wang X . Medical textiles as vascular implants and their success to mimic natural arteries. J Funct Biomater. 2015; 6(3): 500-525.

[5] Pansadoro V, Scarpone P, Emiliozzi P . Treatment of a recurrent penobulbar urethral stricture after wallstent implantation with a second inner wallstent. Urology. 1994; 43(2): 248-250.

[6] McIntee BE . The wallstent endoprosthesis. Gastrointest Endosc Clin N Am. 1999; 9(3): 373-381.

[7] Sousa AM, Amaro AM, Piedade AP . Structural design optimization through finite element analysis of additive manufactured bioresorbable polymeric stents. Mater Today Chem. 2024; 36: 101972.

[8] Zhao J, Zhang S, Duan L, Yao R, Yan Y, Wang T, et al. Preparation and mechanical optimization of a two-layer silk/magnesium wires braided porous artificial nerve guidance conduit. J Biomed Mater Res A. 2022; 110(11): 1801-1812.

[9] McKenna CG, Vaughan TJ . An experimental evaluation of the mechanics of bare and polymer-covered self-expanding wire braided stents. J Mech Behav Biomed Mater. 2020; 103: 103549.

[10] Duda SH, Wiskirchen J, Tepe G, Bitzer M, Kaulich TW, Stoeckel D, et al. Physical properties of endovascular stents: An experimental comparison. J Vasc Interv Radiol. 2000; 11(5): 645-654.

[11] Farooq J, Lee JY . Vascular tortuosity in endovascular mechanical thrombectomy. Brain Circ. 2021; 7(1): 3-7.

[12] Cagnazzo F, Cappucci M, Lefevre PH, Dargazanli C, Gascou G, Morganti R, et al. Treatment of intracranial aneurysms with self-expandable braided stents: A systematic review and meta-analysis. AJNR Am J Neuroradiol. 2018; 39(11): 2064-2069.

[13] Salamaga S, Stępak H, Żołyński M, Kaczmarek J, Błaszyk M, Stanišić MG, et al. Three-year real-world outcomes of interwoven nitinol supera stent implantation in long and complex femoropopliteal lesions. J Clin Med. 2023; 12(14): 4869.

[14] Yang N, Huang W, Lin J, Chen Y, Wu Z, Jiang Y, et al. Stable and integrated nanocellulose-covered stents via in situ microbial synthesis. Adv Funct Mater. 2025; 35(34): 2415272.

[15] Xue W, Lin J, Wang F, Li Q, Wang L . Design and mechanical behaviors of sutureless prototype composite nitinol stent-grafts. Text Res J. 2018; 88(13): 1517-1530.

[16] Liu G, Zhang P, Wang W, Yang J . Study on braiding parameters of braiding nerve conduit. J Donghua Univ Nat Sci. 2003; 29(6): 5.

[17] Kelly N, McGrath DJ, Sweeney CA, Kurtenbach K, Grogan JA, Jockenhoevel S, et al. Comparison of computational modelling techniques for braided stent analysis. Comput Methods Biomech Biomed Engin. 2019; 22(16): 1334-1344.

[18] Li C, Wang X, Zhao F, Wang F, Ting Z, Wang L . Modeling of braiding parameter impact on pore size and porosity in a tubular braiding fabric. E Polym. 2017; 17(3): 221-226.

[19] Qiu X, Gu X, Liu C, Tian H, Chen R, Li Y . Influence of geometric parameters on partial compressive force and pushing performance of flow diverter. Int J Numer Method Biomed Eng. 2022; 38(2): e3553.

[20] García A, Peña E, Martínez MA . Influence of geometrical parameters on radial force during self-expanding stent deployment. Application for a variable radial stiffness stent. J Mech Behav Biomed Mater. 2012; 10: 166-175.

[21] Shang Z, Ma J . Bending stiffness characterization of braided stent using spring-based theoretical formula. Arch Appl Mech. 2023; 93(3): 947-960.

[22] Lucchetti A, Juhl LG, Corti A, Zaccaria A, Gries T, Chiastra C, et al. From bench testing to virtual implantation: A comparative study between poly-l-lactic acid and nickel-titanium braided stents. Int J Numer Method Biomed Eng. 2025; 41(8): e70078.

[23] Kim JH, Kang TJ, Yu WR . Mechanical modeling of self-expandable stent fabricated using braiding technology. J Biomech. 2008; 41(15): 3202-3212.

[24] Boris D, Xavier L, Damien S . The tensile behaviour of biaxial and triaxial braided fabrics. J Ind Text. 2018; 47(8): 2184-2204.

[25] Jedda H, Ben Abdessalem S, Ragoubi M, Sakli F . Contribution to the optimisation of artificial ligament mechanical properties. J Text Inst. 2008; 99(3): 273-280.

[26] Lu X, Zhao S, Chen W, Xie H, Teng J, Ren L, et al. Bioinspired multilayer braided structure with controllable nonlinear mechanical properties for artificial ligaments. Mater Des. 2024; 241: 112976.

[27] Xiao S, Lanceron C, Wang P, Soulat D, Gao H . Mechanical and thermal behaviors of ultra-high molecular weight polyethylene triaxial braids: The influence of structural parameters. Text Res J. 2019; 89(16): 3362-3373.

[28] Zhang Z, Xiong Y, Hu J, Guo X, Xu X, Chen J, et al. A finite element investigation on material and design parameters of ventricular septal defect occluder devices. J Funct Biomater. 2022; 13(4): 182.

[29] Alpyildiz T . 3D geometrical modelling of tubular braids. Text Res J. 2012; 82(5): 443-453.

[30] Rawal A, Gupta S, Saraswat H, Sibal A . Geometrical modeling of near-net shape braided preforms. Text Res J. 2015; 85(10): 1055-1064.

[31] Kamenskiy A, MacTaggart J, Desyatova A . Computational optimization of a stent for the femoropopliteal artery. Ann Biomed Eng. 2026; 54(5): 1287-1305.

[32] Wei L, Chen N, Yang H, Zheng Z, Dong N, Guo H, et al. The data of Chinese minimally invasive cardiovascular surgery in 2019. Chin J Clin Thorac Cardiovasc Surg. 2019; 28(2): 149-153. Chinese.

[33] Wang S, Zhang X, Li J, Liu C, Guan S . Investigation of Mg-Zn-Y-Nd alloy for potential application of biodegradable esophageal stent material. Bioact Mater. 2020; 5(1): 1-8.

[34] Heieck F, Hermann F, Middendorf P, Schladitz K . Influence of the cover factor of 2D biaxial and triaxial braided carbon composites on their in-plane mechanical properties. Compos Struct. 2017; 163: 114-122.

[35] Zheng Q, Dong P, Li Z, Lv Y, An M, Gu L . Braided composite stent for peripheral vascular applications. Nanotechnol Rev. 2020; 9(1): 1137-1146.

[36] Rebelo R, Vila N, Fangueiro R, Carvalho S, Rana S . Influence of design parameters on the mechanical behavior and porosity of braided fibrous stents. Mater Des. 2015; 86: 237-247.

[37] Zhu DM, Du Y, Lu GY, Cheng Z . Mechanical behavior of a new stent with negative poisson’s ratio: The influence of geometric parameters. J Mech Med Biol. 2024; 24(6): 2350108.

[38] Liu M, Tian Y, Cheng J, Zhang Y, Zhao G, Ni Z . Mixed-braided stent: An effective way to improve comprehensive mechanical properties of poly (L-lactic acid) self-expandable braided stent. J Mech Behav Biomed Mater. 2022; 128: 105123.

[39] Feng H, Shi X, Wang T, Wang K, Su J . A comparative study on the deformation behavior and mechanical properties of new lower extremity arterial stents. Comput Methods Programs Biomed. 2024; 247: 108094.

[40] Yang M, Du Y, Zhu D, Wu X, Liu G . Bending flexibility of negative Poisson’s ratio structural vascular stent. J Biomech Eng. 2025; 147(5): 051006.

[41] Shen X, Chen J, Xu Y, Liu Q, He Z, Wang L, et al. Torsional behavior of peripheral vascular stents: The role of stent design parameters. Proc Inst Mech Eng H. 2025; 239(2): 121-132.

[42] Ubachs R, van der Sluis O, Smith S, Mertens J . Computational modeling of braided venous stents - Effect of design features and device-tissue interaction on stent performance. J Mech Behav Biomed Mater. 2023; 142: 105857.

[43] Zhao Y, Cui H . Finite element analysis of braided dense-mesh stents for carotid artery stenosis. Comput Methods Biomech Biomed Engin. 2024; 27(5): 609-619.