The foot flexion of the MR-LF and the MR-DF control was compared using physical half-robot models mounted at a set location (x = 0, ya = 11 cm) in the magnetic field of the actuator magnet. Data of the foot flexion angle across the actuator magnet orientation and images of the maximum and minimum angles are shown in Figure \ref{882568}. The minimum foot flexion of both models was the same (θf = -21.1°), while the maximum flexion of MR-DF (23.4°) was slightly higher than MR-LF (21.2°). The MR-LF data closely match MR-DF across the entire actuator magnet rotation, which indicates that the methods to localize body flexibility were successful at reducing the bending region length while preserving foot flexion. The slight increase of maximum angle for MR-DF (10%) was expected, as the longer bending length of the MR-DF model caused the foot to be closer to the actuator magnet and thus experience a higher magnetic field strength than the MR-LF model. The  difference could also be caused by expected imperfections in the model placement or simplifications in the theoretical calculations, such as neglecting the effect of bending in the material used to join the soft MR-LF flexure and rigid compartment.
A comparison of small-scale, flexible magnetic robots is included in Table S1 in Supporting Information. In contrast to our work, the prior robots have not leveraged localized flexibility to create a centralized compartment that is capable of enhancing the robot’s functionality without affecting its gait or increasing its form factor.