3D printed auxetic stents with re-entrant and chiral topologies

The mechanical performance of the medical stent is crucial and of key significance to the dependability and reliability of the stent-plaque-artery system. In this study, an auxetic stent, namely, re-entrant chiral auxetic (RCA) is proposed. Two types of stent (RCA-X and RCA-Y) are proposed. The RCA stents are designed through a periodic distribution of two dimensional (2D) RCA cells along both the circumferential and axial directions. A set of polyimide specimens were 3d printed using Multi-Jet Fusion process. The compressive properties of the 3d printed stents were experimentally examined, while the tensile properties were numerically investigated. Results showed that the RCA-X stent revealed a remarkable radial expansion (i.e. auxetic features) of approximately 50% while the RCA-Y stent showed radial expansion of 16.7%. Despite the auxetic features of the compressed stents, asymmetric deformation patterns were resulted in the case of the RCA-X while uniform patterns were resulted in the case of the RCA-Y. The FE models were further employed to examined the effects of number of unit cells along the circumferential direction on the auxetic features. The auxetic features of the developed stents could be controlled by adjusting the geometric parameters of the RCA’s cell and number of cells along the circumferential direction. The promising properties of the RCA stents might sheds the light on the design auxetic stents for practical clinical applications.