Design of FFF-Processable Thermo-Magneto-Responsive PLA Nanocomposites for Remotely Actuated Shape Morphing

Thermo-magneto-responsive soft materials, composed of polymer matrices embedded with magnetic particles, are promising for smart systems capable of controlled shape morphing under alternating magnetic fields (AMFs) via localized heating. This study examines how synthesis method (solvent-assisted polymer dissolution vs. temperature-induced softening), magnetic filler type (FeNi, γ-Fe2O3, CoFe2O4), and loading percentage (10–30 wt.%) influence the self-heating performance of polylactic acid (PLA) nanocomposites, a biocompatible polymer widely used in fused filament fabrication (FFF). All formulations retain the magnetic properties of bare particles, with saturation magnetization increasing proportionally to filler content. FeNi- and γ-Fe2O3-based PLA nanocomposites exhibit the highest temperature increase under AMFs maintained within physiologically tolerable levels for potential biomedical use. At 20 wt.% loading, γ-Fe2O3/PLA demonstrates better heating efficiency, whereas FeNi/PLA exhibits superior temperature increases at higher filler concentrations. To demonstrate practical feasibility, FeNi/PLA filaments were successfully extruded and processed via FFF to produce structures specifically designed for controlled shape morphing. Shape-recovery experiments under AMFs confirm that the printed object can be reliably actuated, providing proof-of-concept validation for the functional application of these composites. Overall, these findings provide practical guidelines for the design of thermo-magneto-responsive PLA nanocomposites by balancing heating efficiency, FFF processability, and human-safe AMF operating conditions.