3D Printing of Self‐Healing Polymers by Material Extrusion: A Process‐Centric Review of Setups, Parameters, and Applications

Additive manufacturing (AM) has become a key technology for fabricating complex and functional structures. Among AM techniques, material extrusion (MEX), including both filament‐based and ink‐based approaches, is particularly attractive due to its cost‐effectiveness, broad material compatibility, hardware customizability, and scalability. However, MEX‐fabricated structures often suffer from mechanical and functional limitations, such as poor interlayer adhesion, microcrack formation, and fatigue‐induced damage, which limit long‐term durability and performance. Self‐healing (SH) materials, capable of autonomously repairing damage, offer a promising strategy to overcome these challenges. While existing reviews on SH systems primarily focus on material chemistry and polymer science, this work shifts the emphasis to the MEX 3D printing process itself. This review classifies MEX technologies into filament‐based and ink‐based methods and provides a systematic overview of strategies to enhance the printability and performance of SH materials. These strategies are grouped into three categories: (i) hardware customization, (ii) optimization of printing strategies and parameters, and (iii) postprocessing to improve SH efficiency. Special attention is given to emerging multi‐material extrusion (M‐MEX), highlighting SH architectures for embedded electronics, stiffness‐graded components, and multifunctional systems with autonomous repair. Finally, future directions are discussed, emphasizing manufacturing hybridization and closed‐loop real‐time control to further advance MEX‐based SH devices.