UV, UV-Vis and NIR Photoinitiators in Light-Based 3D Printing Processes

light-based three dimensional (3D) printing processes which are based on the use of light-sensitive monomers or oligomers, are the most versatile and interesting technique due to the unique potential to design structures with complex geometry, the ease of the process, the availability of the required compounds as well as the feasibility of tailoring materials to achieve the required properties. In this approach, photoinitiators are considered the key elements in the success of this process, and several types of research have been performed to introduce initiators with enhanced efficiencies. This article reviews the types of photoinitiators used in 3D printing technology and highlights the research carried out to transfer the absorption region of the compounds from the ultraviolet region to the visible region. In addition, water-soluble photoinitiators are also of great interest for use in the bioprinting of hydrogel systems, which are reviewed in this article. Obviously, success in the development of the 3D printing process and fabrication of constructs with suitable mechanical properties as well as resolution requires familiarity with the key elements involved in the process, therefore, one of the most important factors is investigated