Mechanical characterizations of braided composite stents made of helical polyethylene terephthalate strips and NiTi wires

Abstract

The novel braided composite stent (BCS), woven with both nitinol wires and polyethylene terephthalate (PET) strips, were characterized and compared with the braided nitinol stent in the same weaving pattern. Finite element models simulating the stent compression and bending were developed to quantify its radial strength and longitudinal flexibility. The interaction between the nitinol wires and the PET strips were also delineated. Results showed that the PET strips enforced more constrains on the BCS and thus enhance its radial strength especially at a larger compression load. The longitudinal flexibility of the BCS was less sensitive to the presence of the PET strips. This work suggested that the novel design of the BCS could acquire the advantage of a covered stent without compromising its mechanical performance. The fundamental understanding of the braided composite stent will facilitate a better device design.

Braided composite stent for peripheral vascular applications

“…The validation of the BCS models had been conducted in our previous work [25]. The radial strength of the stent was evaluated while compressing the stent to 50% of the original diameter of 7 mm, and the numerical result agreed well with the experimental result [25,30]. The surface coverage, the compression load, and the bending moment for all eight cases are summarized in Table 4.…”

“…The influence of factor difference between two stents can be explained by the unique structure of BCS. In BCS, the presence of wide PET strips can constrain the sliding of the nitinol wires and enhance the radial strength of the stent at the large deformation, the radial strength was 52% larger than that of the BNS at the deformation of 50% original diameter [25]. Due to the interaction between the nitinol wire and PET strips, the structure of BCS tends to be more stable.…”

“…After that the bending moment is mainly borne by nitinol wires. BCS exhibits better flexibility than the BNS and the covered stent at a small bending angle, i.e., the bending angle at 30° [25,29].…”

“…Recently, a novel braided composite stent (BCS) was proposed to combine the merits of both braided stent and covered stent for achieving the desirable radial strength, flexibility, and increased surface coverage [25]. It was made of nitinol wires and polyethylene terephthalate (PET) helical strips.…”

“…Specifically, it was reported that the bending moment of the BCS was 17.4% smaller than that of the covered stent when subjected to a bending angle of 30° [25,29]. The presence of wide PET strips of BCS can constrain the relative displacement of the nitinol wires and enhance its radial strength at a large deformation [25,30]. The parameters such as nitinol wire diameter, initial braiding angle, and strip thickness are essential to the mechanical performance of the BCS.…”