Multi-material and Multi-dimensional 3D Printing for Biomedical Materials and Devices

In recent years, Additive Manufacturing (AM) has evolved into a “multi-x” era, such as multi-part design, multi-material, multi-process, multi-mode, multi-scale, multi-dimension, and multi-function. These emerging new features of AM present both tremendous opportunities and challenges for developing and regulating new and novel biomedical materials and devices. This paper focuses on two aspects, namely multi-material and multi-dimension AM. In multi-material 3D printing, the layering step is the key. Modifying the layering method yet without changing the solidifying or bonding principles governing the AM process can enable and significantly advance multi-material 3D printing. In multi-dimensional 3D printing, typically 4D printing and 5D printing, the meaning of “D” is suggested to refer to space–time dimension rather than the number of degrees of freedom in physical space. It is proposed in this paper that an alternative dimension (or 5D) for future 3D printing processes can be that of scale. Scale here refers the different levels of resolution that are used simultaneously within a print. In such a scale dimension, continuous printing of cross-scale or varied resolution design features in a single build process without affecting the overall printing speed and time would be highly desirable. This is probably the first paper reflecting on multi-material 3D printing from the perspective of layering and on multi-dimensional 3D printing with regard to its future development.