Multi-Objective Optimizations of Biodegradable Polymer Stent Structure and Stent Microinjection Molding Process.

Hongxia Li,Zheng Li,Minjie Wang,Danyang Zhao,Yahua Liu,Junfeng Gu,Aike Qiao,Yunbo Wei,Tao Liu,Xinyu Wang

doi:10.3390/polym9010020

Hongxia Li, Zheng Li + Show 8 more

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https://doi.org/10.3390/polym9010020

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Abstract

Biodegradable stents made of poly-l-lactic acid (PLLA) have a promising prospect thanks to high biocompatibility and a favorable biodegradation period. However, due to the low stiffness of PLLA, polymeric stents have a lower radial stiffness and larger foreshortening. Furthermore, a stent is a tiny meshed tube, hence, it is difficult to make a polymeric stent. In the present study, a finite element analysis-based optimization method combined with Kriging surrogate modeling is firstly proposed to optimize the stent structure and stent microinjection molding process, so as to improve the stent mechanical properties and microinjection molding quality, respectively. The Kriging surrogate models are constructed to formulate the approximate mathematical relationships between the design variables and design objectives. Expected improvement is employed to balance local and global search to find the global optimal design. As an example, the polymeric ART18Z stent was investigated. The mechanical properties of stent expansion in a stenotic artery and the molding quality were improved after optimization. Numerical results demonstrate the proposed optimization method can be used for the computationally measurable optimality of stent structure design and stent microinjection molding process.

Highlights

Astent is a tiny mesh tube used to treat arterial occlusive diseases, with an angioplasty procedure performed to partially open up the blocked vessel
The initial trial samples, including an initial experience design and another 30 samples generated by optimal Latin hypercube sampling (LHS), were selected for constructing Kriging surrogate model
The warpage of warpage of the optimal design was reduced by 28.3%, which was helpful to improve the molding thequality optimal was distribution reduced by 28.3%, whichofwas to improve molding quality stent

Summary

Introduction

Astent is a tiny mesh tube used to treat arterial occlusive diseases, with an angioplasty procedure performed to partially open up the blocked vessel. After being positioned in a stenosis segment, the stent is expanded radially under the action of balloon expansion. Once the balloon is deflated and removed, the expanded stent retains its diameter and provides a scaffoldlike support structure to maintain the patency of the vessel, thereby promoting blood flow. There are three development stages of stents: bare-metal stents (BMS), drug-eluting stents (DES), and bioresorbable stents. Bioresorbable stents, which can address the concerns raised by permanent metallic stents (e.g., long-term safety), is considered to be the fourth revolution in interventional cardiology [1].

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