Magnetocaloric actuation of soft polymer robots

The magnetocaloric effect can be used to achieve remote manipulation of soft polymer actuators for shape-programmable actuation, which plays a key role in multifunctional applications in robotics. We herein report a polymer bilayer actuator composed of an inert poly(vinylidene fluoride) (PVDF) layer and a thermal-expansive polydimethylsiloxane (PDMS) layer. Fe(0) particles (100-500 nm) were hybridized into the PDMS layer to transduce magnetic effects into heat energy. Upon exposure of the bilayer actuator to an electromagnetic field, the strong magnetocaloric effect enabled its temperature to rapidly rise to 72 °C in 4 s. At this temperature, the volume of the PVDF layer remained constant, while the PDMS@Fe layer expanded by 2.5%. This asymmetric expansion provided a theoretical basis for motility of soft polymer robots. As a result of patterning designs to endow the material with spatially-asymmetric magnetocaloric effects, the polymer robots were capable of undergoing various motions with controllable kinematics, showing a promising potential in magnetocaloric robotics.