C. Barner-Kowollik, M. Bastemeyer, E. Blasco, P.  Mueller, G. Delaittre, B. Richter, and M. Wegener

Angew. Chem. Int. Ed. (2017); doi:10.1002/anie.201704695

3D printing is a powerful emerging technology for the tailored fabrication of advanced functional materials. The current review summarizes the state-of-the art with regard to 3D laser micro- and nano-printing and explores the critical chemical challenges limiting its full exploitation. These challenges are rationalized in five categories spanning the development of advanced functional materials for applications in cell biology and electronics to the chemical barriers that need to be overcome to enable fast writing velocities while enabling sub-diffraction coding. Further, we explore chemical means which would enable multi-material direct laser writing from one resist, based on highly wavelength selective (so-called λ-orthogonal) photochemical processes. Finally, chemistries to construct adaptative 3D written structures, able to respond to external stimuli such as light, heat, pH, or specific molecules, are highlighted, and advanced concepts for degradable scaffolds are explored. Our article thus not only serves as a compendium of the current state in 3D laser printing, yet also identifies the critical barriers that need to be overcome to enable the next generation of micro- and nano-sized 3D materials.