Braiding structure stability and section treatment evaluations of braided coronary stents made of stainless steel and bio-absorbable polyvinyl alcohol via a braiding technique

Abstract

To simplify the manufacturing process of coronary stents, this study employs a braiding technique that uses metallic and polyvinyl alcohol (PVA) fibers to prepare the metallic and PVA coronary stents. 316L stainless steel (SS) fibers and PVA fibers are respectively made into single- and double-ply braids, during which the gear ratios of the take-up gear to the braid gear are changed to 50:50, 60:50, 70:50, 80:50, and 90:50. The braiding structure is then bonded and stabilized by using a PVA solution, after which stereomicroscope observation, scanning electron microscopic (SEM) observation, braiding angle analysis, and strut cover rate measurement are performed to test the SS and PVA coronary stents. The experimental results show that the braiding technique can prepare the SS and PVA braids with the required braiding structure. However, cutting causes the braiding structure of the SS braids to expand due to the properties of the SS fibers while the PVA braids are too soft to take the form of a hollow tube. Therefore, a PVA solution coating is applied to stabilize the structure in order to complete the preparation of the SS and PVA coronary stents. Braiding angle decreases when the tooth number on the take-up gear decreases; furthermore, the strut cover rate and fiber diameter and area have a positive correlation. This study successfully combines a braiding technique and PVA solution coating to create SS and PVA coronary stents that present a stable braiding structure after cutting.