Advancing multi-stimuli 4D printing of polylactic acid with rapid shape memory and enhanced toughness using lignin-coated Fe3O4 nanoparticles

The combination of multi-stimuli-responsive shape memory composites and 3D printing provides greater flexibility and precision to create innovative and smart products controlled by non-contact methods, offering new opportunities. Here, the thermal/magnetic/light-triggered multi-stimuli responsive shape memory polymer composite with well-balanced strength and toughness was prepared by adding Fe3O4 magnetic nanoparticles into poly(lactic acid)/ poly(propylene carbonate) polyurethane composite. The composite exhibited excellent shape memory behavior, high shape recovery rate, fast response behavior, and good shear thinning behavior suitable for application in 3D printing. The obtained results revealed the versatility of easily fabricated and low-cost filaments. Dynamic, remote, and precise control of 4D transformations can be achieved through controllable external stimuli, such as magnetocaloric effects in alternating magnetic fields or photothermal effects in nearinfrared light. This work provided important references and foundations for the design of smart materials and devices.