An analytical solution for the stress state at stent-coating interfaces

In this paper an analytical solution for the stress state in a coated stent is presented, with a particular focus on the interface stresses between the coating and stent. As a first step a simplified stent architecture consisting of a bi-layered composite elastic arch is considered. The variations of normal and shear stress at the interface as functions of the boundary conditions at the base of the arch are explored. Depending on applied displacement and rotation, very distinct distributions of stress occur along the interface: dominant shear or dominant normal stress, compressive or tensile normal stress. A bi-layered composite elastic strut is then added to the composite elastic arch in order to create a realistic coated stent geometry. A displacement is applied to the bottom of the strut to simulate stent deployment. The addition of the strut is found to increase the normal stress and decrease the shear stress at all points on the interface. The influence of the various geometrical and material parameters on interface stress is explored using the analytical procedure developed in the paper, providing practical insight for stent-coating design.