Fdm-based 4D printed polymer blends: characteristics and applications

Shape memory polymers are a distinct category of intelligent materials that can change their configuration in response to external stimuli, such as moisture, light, or temperature. 4-dimensional (4D) printing offers the advantages of 3-dimensional printing and shape-memory capability. The use of polymer blends offers an effective strategy to enhance the overall shape memory effect, including improvements in shape recovery, shape fixity, response time, and recovery speed, while simultaneously tailoring mechanical performance. This review presents a comprehensive overview of material selection, blend composition, and relationships between structure, properties, and stimuli in fused deposition modeling (FDM)-based 4D-printed polymer blends. The key characterization techniques used to assess thermal, mechanical, and shape-memory behaviors are critically discussed. Recent advances in polymer blend systems, including PLA, PETG, TPU, PCL, and ABS-based blends, are reviewed. Further, their emerging applications in biomedical devices, soft robotics, aerospace, and smart structures are discussed. Finally, the current challenges in printability, interfacial compatibility, rheology, and reproducibility, along with future research directions, are outlined to advance FDM-based 4D printed polymer blend systems.