Multi-Material Implant Structures with Medical-Grade Polyurethane via Additive Manufacturing

Additive Manufacturing (AM) allows the creation of personalized medical models, tools, and implants. Patient-specific structures can be fabricated faithfully, quickly and reliably. The production of orthopedic implants by means of AM could greatly benefit from multi-material structures. The skeletal system is composed of hard bones and softer cartilage, performing different tasks in the body. Multi-material implant structures require biocompatible materials that can withstand in-body conditions for extended periods of time. Among possible material candidates, polyurethanes have been selected for further investigation. This project studied two medical-grade polyurethanes (with established clinical history for long-term implants) produced by DSM Biomedical with a Shore hardness of 75D and 80A. They were used to fabricate three-dimensional structures with the thermoplastic material jetting technique (MJT) known as Arburg Plastic Freeforming (APF). Tensile and bending specimens were produced for the individual polyurethanes by applying optimized processing parameters. Also, multi-material specimens were manufactured to analyze fracture failure at the interface between the two polyurethanes in tension. Based on information collected in this investigation, recommendations on preparing implantable structures such as rib replacement systems, are given.