4D Printing of Magneto-Thermo-Responsive PLA/PMMA/Fe3O4 Nanocomposites with Superior Shape Memory and Remote Actuation

This study presents the development and 4D printing of magnetic shape memory polymers (MSMPs) utilizing a composite of polylactic acid (PLA), polymethyl methacrylate (PMMA), and Fe₃O₄ nanoparticles. The dynamic mechanical analysis reveals that the integration of Fe₃O₄ maintains the broad thermal transition without significantly affecting α-relaxation time, indicating high compatibility and homogeneous distribution of the nanoparticles within the polymer matrix. Field emission scanning electron microscopy further confirms the high compatibility of PLA and PMMA phases as well as uniform dispersion of Fe₃O₄ nanoparticles, essential for the effective transfer of heat during the shape memory process. Significantly, the incorporation of magnetic nanoparticles enables remote actuation capabilities, presenting a substantial advancement for biomedical applications. 4D-printed MSMP nanocomposites exhibit exceptional mechanical properties and rapid, efficient shape memory responses under both inductive and direct heating stimuli, achieving 100% shape fixity and 100% recovery within ≈85 s. They are proposed as promising candidates for biomedical implants, specifically for minimally invasive implantation of bone scaffolds, due to their rapid remote actuation, biocompatibility, and mechanical robustness. This research not only demonstrates the 4D printability of high-performance MSMPs but also introduces new possibilities for the application of MSMPs in regenerative medicine.