4D Printing of Magnetic Shape Memory Polymer—La0.7Sr0.3MnO3 Nanocomposite

Abstract

Four-dimensional printing has revolutionized traditional three-dimensional printing (3D printing) by using smart materials such as shape memory polymers (SMPs). As nonmagnetic materials, SMPs require direct exposure to heat for the shape memory effect to be triggered. This limitation can be addressed by incorporating magnetic nanoparticles, allowing the SMP/nanocomposite to be remotely heated through induction heating. This work focuses on the ${\text{La}}_{1-x}{\text{Sr}}_x{\text{MnO}}_3$ (LSMO) manganite with an optimized stoichiometry of x = 0.3. Polycrystalline LSMO is sintered from pure powders and later added to SMP through the solution mixing route, and finally extruded into filaments to be used for 3D printing. Significant improvements in the elastic modulus, yield, and ultimate strengths are observed following LSMO addition. All the composites exhibit magnetic moments near 3.5 μ_B Mn⁻¹ at the ground state indicating desirable magnetic properties. Shape memory properties are evaluated following the application of programming and recovery cycles on the as-printed single-cell auxetic structure. The evaluation of the bulk strain on the auxetic structure for 0 and 20 wt% LSMO/SMP nanocomposite reveals no change in shape fixity, a slight decrease in shape recovery ratio from 88 to 81%, and a significant improvement in the shape recovery rate from 124.3 to 179.5% min⁻¹.