Strategies to Improve Water Solubility of Photoinitiator for Photopolymerization-Based 3D Printing in Biomedical Applications

3D printing has gained significant importance in biomedical applications due to its capability to create intricate, biocompatible structures with high precision. Among the various 3D printing techniques, vat photopolymerization (VPP) stands out for its rapid molding speed, smooth surface finish, and exceptional accuracy. A critical component in the VPP printing process is photoinitiators (PIs), which trigger polymerization by generating free radicals under light exposure. However, many PIs face challenges due to poor water solubility, leading to issues such as uneven printing, particularly in tissue engineering applications. This review offers a concise yet comprehensive overview of strategies to enhance the water solubility of PIs and their applications in VPP-based 3D printing. We begin by introducing different types of PIs and their initiation mechanisms, followed by a summary of recent strategies for improving their water solubility. We then explore the use of water-soluble PIs in 3D-printed biomedical materials and conclude with insights into future directions and potential advancements in the field, providing guidance for the design and optimization of water-soluble PIs.