4D printing in the medical sector: current trends and future narrative

Applications of 3D printing in medicine are already well-established in relation to utilizing the shape freedom provided by additive manufacturing and capabilities of the digital pathway from the idea and clinical image to a product. Today's attention to designing 3D-printed parts for medicine and veterinary applications has shifted from pure “designing for defined shape” to the addition of “designing for demanded functionality.” Here additional properties or functionalities invoked into the final part beyond spatial ones (three dimensions), such as specific physical, biological, electrical, magnetic, or other functional parameters effectively that expand the design space toward the fourth functional dimension. In this chapter, the authors attempt to show the trends in functionalization of case- and patient-specific implants and supporting medical tools, including the specifics of the approaches (e.g., metamaterial), specific design modalities, and manufacturing methods. The chapter will cover materials, design, and manufacturing of porous structures (including variations of porosity, layered, and gradient structures), surface structuring, and functionalization. It has also focused on the integration of 3D printing into the surgery flow (parts for preoperational planning, customization of tools, physical modeling of human body parts), digital and physical modeling of the components functioning in the body, their stability, and longevity.