Development and 4D printing of magneto-responsive PMMA/TPU/Fe3O4 nanocomposites with superior shape memory and toughness properties

• Innovative 4D printed PMMA/TPU/Fe3O4 nanocomposites. • Magneto-responsive shape memory properties. • Enhanced toughness with TPU addition. • Fast shape recovery in magnetic fields. • Successful 3D printed gripper demonstration. This paper introduces 4D printing of composites of polymethyl methacrylate (PMMA) and thermoplastic polyurethane (TPU) reinforced with Fe 3 O 4 particles for the first time. PMMA/TPU blends with 70/30 wt% are selected as matrix with the best compatibility based on dynamic mechanical thermal analysis. Fe 3 O 4 nanoparticles are added to the blends with 10 %, 15 % and 20 % weight ratios. Their addition enables remote actuation of the materials in a high frequency alternating magnetic field. Field emission scanning microscopic images confirms a full dispersion of nanoparticles inside the polymeric matrix. Nanocomposites with 20 wt% of Fe 3 O 4 can perfectly recover the permanent shape within 1.5 min in the magnetic field. They also reveal perfect shape memory properties in the hot water. Moreover, all samples display a perfect shape fixity ratio. The addition of TPU significantly enhances the toughness and flexibility of the PMMA matrix. It is found that Fe 3 O 4 nanoparticles further enhance the mechanical strength by 10 % to 15 %, although they reduce the strain at break from 17 % to 14 %. Finally, a gripper is 4D printed and its excellent performance in the magnetic field is demonstrated.