The current versatility of polyurethane 3D-printing for biomedical applications.

Reconstructive surgery aims to restore tissue defects by replacing them with similar autologous tissue to achieve good clinical outcomes. However, often the defect is too large or the tissue available is limited requiring synthetic materials to restore the anatomical shape and partial function. The utllisation of three-dimensional (3D) printing allows for the manufacture of implants with complex geometries and internal architectures that more closely match the clinical requirements needed. Synthetic polymers offer certain advantages over natural polymers as biomedical materials due to their ability to more closely mimic the mechanical and chemical properties of the native tissue. Synthetic polymer materials such as Poly(lactic Acid) (PLA), Acrylonitrile butadiene styrene (ABS) are easily 3D printed to generate 3D objects due to their flexibility in their chemical and mechanical properties and physical form. Polyurethanes are widely used as short- and long-term implantable medical devices due to their good mechanical properties, biocompatibility and haemocompatibility. This article provides an overview on the advancement 3D printable polyurethane-based materials for biomedical applications. A summary of the chemical structure and synthesis of polyurethanes is provided to explain how polyurethanes may be processed into medical devices using additive manufacturing techniques. Currently polyurethanes are being explored by several 3D printing approaches including fused filament fabrication (FFF), bioplotting and sterolithography (SL) to fabricate complex implants with precise patterns and shape with fine resolution. Scaffolds using 3D printing polyurethanes have shown good cell viability and tissue integration in vivo. The important limitations of polyurethane printing are identified to stimulate future research. Polyurethanes offer a biocompatible synthetic polymeric material that can be 3D printed to manufacture implants, which are tailored to meet specific anatomical, mechanical and biological requirements for biomedical applications.