4D printing of Nd-Fe-B composites with both shape memory and permanent magnet excitation deformation

Novel composite filaments are developed by mixing PLA, TPU, and Nd-Fe-B components and utilizing melt extrusion for 4D printing. The results reveal that the Nd-Fe-B magnetic particles are uniformly dispersed in the PLA/TPU polymer matrix, and the composite filaments meet the requirements of high-precision printing. Increasing the proportion of Nd-Fe-B magnetic particles in the composite contributes to higher remanence, coercivity, and magnetic energy product for the printed magnets. Under the 70 °C thermal stimulus, it has a high shape fixed ratio (>99 %), a high shape recovery ratio (>90 %), and a rapid response time (≤6.55 s). The magnetic particles accelerate the shape recovery process. Moreover, the petal-like structure and the hollow ball structure are designed and printed. After deformation, each structure can nearly fully recover its initial shape. This recovery is achieved through a non-contact stimulus response based on 'thermal-magnetic' coupling. The grippers printed by the developed composite show comprehensive properties of shape memory and magnetically controlled smart gripping.