Design and fabrication of multifunctional shape memory PETG/Fe 3 O 4 nanocomposites for thermally triggered shape-memory switch

Magnetically responsive shape-memory polymer composites enable the development of advanced sensing and switching systems that can detect thermal, magnetic, and electrical changes. In this study, multifunctional shape-memory PETG/Fe 3 O 4 nanocomposites containing 0.5–4 wt.% Fe 3 O 4 were fabricated by injection molding. The magnetic, electrical, and thermal shape-memory effects of the developed nanocomposites were systematically characterized by vibrating sample magnetometry (VSM), voltage-current (V–I) measurements, and shape recovery tests under hot-water and hot-air conditions. The saturation magnetization (M s ) increased from 0.041 to 0.158 emu/g with increasing Fe 3 O 4 content, confirming successful magnetic functionalization. The composites also exhibited an incremental increase in electrical response with increasing Fe 3 O 4 loading, while remaining electrically insulating. The shape recovery performance was improved by adding Fe 3 O 4 , and the 4 wt.% composite exhibited the shortest recovery time of 41 s and a recovery ratio of 97% in hot water. Finally, a proof-of-concept thermally triggered shape-memory switch was successfully demonstrated, showing the potential of the developed PETG/Fe 3 O 4 nanocomposites for simple thermal switching and smart sensing applications.