Lightweight design and integrated 3D printing of PLA/TPU dual-material orthopedic orthoses

Purpose This paper aims to develop a dual-material orthosis with enhanced comfort, breathability and antibacterial properties to overcome the limitations of current polymeric orthoses that suffer from poor comfort and are prone to bacterial growth during prolonged wear. Design/methodology/approach The experimental approach focuses on the fabrication and evaluation of the dual-material orthosis using integrated multi-material fused deposition modeling. Rigid polylactic acid (PLA) is combined with silver nanoparticles-doped antibacterial flexible thermoplastic polyurethane (TPU). Topology optimization is used to achieve lightweight design, and a parametric study on the PLA/TPU thickness ratio is conducted through comparative experiments. A mechanical interlocking microstructure is introduced at the interface to enhance bonding. Systematic tests are performed to evaluate mechanical strength, impact resistance, interfacial bonding strength and in vitro antibacterial performance. Findings The results of this study demonstrate that the topology-optimized structure achieves a 40% weight reduction while satisfying the required stiffness and strength and forms reasonably distributed ventilation areas. Compared with single-material PLA orthoses, the dual-material orthosis exhibits a 36%–40% improvement in impact resistance and a 20%–25% increase in energy absorption capacity. The interfacial bonding strength reaches 2.05 MPa, ensuring reliable material integration, while the TPU inner layer shows an antibacterial rate exceeding 99%. Originality/value This paper fulfills the practical need to improve the comfort, breathability and hygiene of three-dimensional-printed orthoses. The proposed PLA/TPU orthosis offers a promising design strategy for next-generation personalized orthopedic applications.