Magnetic-responsive robots can achieve remote, rapid, and flexible motion under magnetic field actuation. However, existing magnetic robots are limited by fixed magnetic domains and soft matrices, which restricts their deformability and load-bearing capacity, thus limiting their widespread application in complex environments. In this study, a shape memory composite material is designed with reprogrammable magnetic domains. Through the synergistic action of laser and magnetic fields, the shape memory polymer film is patterned and re-encoded, resulting in various shape-reconfigurable and stiffness-variable opto-magnetic responsive robots. As a result, the limitations of traditional magnetic robots are overcome in terms of limited deformability and weak load-bearing capacity. Moreover, this work provides a new approach for developing adaptive robots capable of performing complex tasks.

The robot is constructed from reprogrammable shape memory composite (RM-SMC), integrating shape memory polymer (SMP) and embedded magnetic microcapsules. These microcapsules, composed of phase-change polymer ethyl vinyl acetate (EVA) encapsulating NdFeB magnetic particles, enable internal magnetic domain reprogramming within the RM-SMC film. Initially, the two-dimensional RM-SMC structure is magnetized in a 1.2 T magnetic field, aligning the magnetic domains along the film thickness direction. Upon near-infrared laser irradiation, the encapsulated NdFeB@EVA microcapsules rapidly absorb heat, causing the EVA to melt at its phase change temperature (90 ℃). This allows the magnetic particles to reorient along the external programming magnetic field (B_p), enabling internal magnetic particle re-encoding. Via subsequent global heating with low-power near-infrared laser, the RM-SMC temperature is increased to its glass transition temperature (T_g), transitioning it to an elastomer. Due to opposite magnetic domains in adjacent areas, the material deforms into a three-dimensional shape under a vertical actuation magnetic field (B_a), with folding deformation occurring along the boundary of these areas. Upon cooling below T_g, the material locks into this three-dimensional shape, maintaining stiffness even after magnetic field removal.

We prepare NdFeB@EVA magnetic microcapsules using a phase separation method and incorporate them into SMP to form the RM-SMC film (Fig. 1). Additionally, we obtain two-dimensional patterns under different designs via laser cutting (Fig. 2). Testing shows that the glass transition temperature of RM-SMC is 77 ℃. Under the combined action of near-infrared laser and external magnetic field, we can encode the anisotropy of magnetic domains within the film. Moreover, the film demonstrates excellent reprogramming and stable deformation capabilities over 100 repeated tests (Figs. 3 and 4). Based on the reprogrammability of RM-SMC films, different torque and torsion directions can be generated by encoding the magnetic domain direction at different positions of the films in response to the driving magnetic field, enabling rapid and reversible transitions between planar and three-dimensional complex structures (Fig. 5). Additionally, this study utilizes the reconstructive deformation and shape-maintenance capabilities of RM-SMC films to prepare magnetic-responsive micro-robots capable of switching among different configurations. The rolling robot can move on flat ground and slopes under the driving of an 80 mT rotating magnetic field, recover its two-dimensional shape as a bridge through heating, as well as withstand a 5 g object (Fig. 6). Further, the cargo robot can transport a 1 g object directionally, while the helical robot can spiral drive in water under the driving of a rotating magnetic field (Figs. 7 and 8).

In this work, reprogramming technology and shape memory polymers are altered to develop a new reprogrammable magnetic shape memory composite material, consisting of NdFeB@EVA magnetic microcapsules and SMP. Through synergistic control of a near-infrared laser and an external magnetic field, insitu encoding of magnetic domains is achieved in a two-dimensional structure. This allows the structure to exhibit various complex three-dimensional shapes, maintaining form without energy consumption, and demonstrating high load-bearing capacity and variable stiffness. This method enables the cost-effective preparation of magnetic-responsive robots capable of freely switching among different configurations and motion modes. Moreover, this advancement not only offers increased flexibility in robot control, but also promises a more convenient and efficient robot operation experience in practical applications. Thus, the developed novel reprogrammable magnetic shape memory robot injects new vitality into the field of robotics and provides strong technical support for achieving higher-level robot control and applications.