Figure 4. Examples of more complex multi-material 3D printing.

A) Schematic demonstrating the workflow of fabricating a multi-layer 3D printed construct. In these multi-material constructs, scaffolds can be fabricated using support materials such as PCL as well as cell-laden hydrogels, and sacrificial materials as discussed in this review. B) Illustration of how the final multi-material print may look using these materials. Reproduced and adapted with permission.^[17] Copyright 2016, Nature Publishing Group. Bottom C–F) examples of more complex multi-material hydrogel printing without a secondary support material. In these examples, up to 7 different bioinks were deposited to create scaffolds with complex spatial designs. In addition, complex features were fabricated even within the organ-like constructs demonstrating the ability to fabricate large hydrogel based scaffolds using multiple materials while maintaining defined spatial control within these scaffolds. Reproduced and adapted with permission.^[31] Copyright 2017, John Wiley and Sons.