Interfacial debonding mechanism in multilayer coated magnesium alloy scaffolds

• Elucidation of the failure mechanism in multi-layer coating interfaces. • Revelation of the critical role of scaffold wall thickness in coating failure. • Development of a multi-parameter optimization strategy to prevent failure. During the deployment of biodegradable magnesium alloy scaffolds, the polymer coating may undergo debonding and delamination due to mechanical strain. While existing studies primarily use single-layer polymers (e.g., PLLA, PCL) on 2D scaffolds, this study employs a PLLA-PDLLA multilayer coating on 3D scaffolds to better characterize deformation behavior and interface failure mechanisms during radial expansion. Results indicate scaffold wall thickness significantly influences coating integrity, with thinner walls reducing strain concentration and delaying delamination. Curvature radius and coating thickness were also identified as critical debonding determinants. Simulation results aligned with SEM observations, validating model accuracy. This work clarifies the multilayer coating failure mechanism, providing a theoretical basis for scaffold optimization and long-term performance enhancement.