4D printing of multi-responsive shape memory polymers: PCL/POE blends with Fe₃O₄ activation via infrared, microwave, and thermal stimuli

Abstract

Abstract Shape memory polymers (SMPs) have gained increasing attention due to their ability to respond to external stimuli, enabling applications in smart materials, biomedical devices, and soft robotics. However, the development of multifunctional SMPs capable of activation through multiple stimuli remains a challenge. In this study, poly( ϵ -caprolactone)/polyolefin elastomer (PCL-POE) composites containing Fe 3 O 4 nanoparticles were developed to achieve multiple activation pathways, including warm water, infrared (IR), and microwave. The composites were prepared via melt blending, incorporating Fe 3 O 4 at different concentrations (15–30 wt%). The shape memory properties were evaluated in different activation modes, and self-healing behavior was investigated at 70 °C. Additionally, the best-performing composition (PCL-POE 30%) was used to produce 3D-printable filaments, which were successfully processed into 4D-printed structures via fused filament fabrication. The results demonstrated excellent shape memory performance across all activation methods, with fixation and recovery rates close to 100% in water, near-infrared, and microwave modes. Higher Fe 3 O 4 content led to faster recovery times, with microwave activation achieving the quickest response (28 s). Moreover, the composites exhibited self-healing behavior, attributed to the thermally induced molecular mobility of the polymer matrix. The 3D-printed structures retained their shape memory properties, enabling 4D printing applications. This study highlights the potential of Fe 3 O 4 reinforced PCL-POE composites for multifunctional smart materials, combining shape memory, self-healing, and printability. Unlike most studies on SMPs, which focus on a single activation method, this work stands out by demonstrating highly efficient responses to three distinct stimuli and is among the few that simultaneously combine 4D printing with multi-stimuli activation at high performance. The ability to activate the shape memory effect through different stimuli expands their applicability in adaptive and programmable materials, making them promising candidates for biomedical, aerospace, and soft robotics applications.