Shape memory polymers enable versatile magneto-active structure with 4D printability, variable stiffness, shape-morphing and effective grasping

Magneto-active structures with non-contact actuation, precise controllability, strong penetrability, and biological harmlessness have wide application prospects in the fields of soft robots, bionic engineering, medical treatment, and flexible transmission, among others. This paper presents the design of a magneto-active shape memory polymer (MASMP) based on a blending matrix of polycaprolactone and thermoplastic polyurethane. The aim is to enhance the environmental adaptability, manufacturability, and diversification of actuation modes of magnetic-active actuators. We conducted an analysis of the magnetic/thermal switchable mechanical properties and shape memory properties of MASMP. The results demonstrate excellent shape fixation and shape recovery rates, as well as excellent flexibility and magnetorheological effects. We fabricated flexible printing filaments with a uniform diameter by using a screw extruder, which enables high-precision 4D printing for MASMP. We printed several magneto-active structures, which demonstrated variable stiffness, shape-morphing, and shape memory capabilities. The shape-morphing performance is in good agreement with the simulation results of the design process. Furthermore, we successfully printed and assembled a flexible claw that exhibits an effective grasping and release function activated by a magnetic field. Finally, we developed a magneto-active structure with negative Poisson’s ratio, showing great potential for application in metamaterial structure.