Novel Cardiovascular Stent Based on Hibiscus-Aestivation-Inspired Auxetic Unit Cell

Conventional stents have some limitations, such as dogboning and foreshortening, that can lead to issues like in-stent restenosis and thrombosis. Negative Poisson's ratio stents, called auxetic stents, are known as a solution to overcome these challenges due to their unique deformation mechanism. Auxetic stents are scale-independent, and their behavior depends solely on their geometry. In this study, a novel auxetic unit cell inspired by aestivation mechanism of the Hibiscus flower is designed, developed, and implemented in plane, and a tube to achieve a novel NPR cardiovascular stent. The stent structure is fabricated using two methods, including a novel 7-axis laser cut method capable of producing stents the same size as human blood vessels from an SS 316L tube, and fused deposition modelling 3D printing at a scale 20 times larger than the metallic sample using PLA filaments. Novel laser cut effectively overcame some challenges in laser cutting stents, including HAZ and thermal shocks. SEM images are taken from the laser cut sample, and the manufacturing method's accuracy and surface quality are investigated. Fabricated metallic and polymeric stent samples proposed negative Poisson's ratio equal to 0.89 with an average of 4.38 and 14.8 % errors, respectively, compared with finite element analysis. Finally, the structure's stress, strain energy distribution pattern, and unit cell distribution have been examined. Furthermore, the stent thickness parameter, drug release patch application, and stent implementation process are also investigated using FEM method. Proposed geometry in stent application showed solutions to conventional positive Poisson's ratio stent challenges.