Fig. 3

Individual foot’s performance in one gait cycle. a Snapshots of an individual foot’s deformation in one gait cycle, which can be divided into four typical stages: controlled dorsiflexion (CD), power plantar flexion (PPF), swing state (SS), and controlled plantar flexion (CPF). b Locomotion curves, including the robot body’s displacement along y axis (pink square line), the foot’s displacement along y axis (green circle line), the robot body’s displacement along z axis (light blue regular triangle line), and the foot’s deformation (dark blue inverted triangle line). The robot can maintain a smooth transition among four different stages in each gait cycle, which is reminiscent of that of human being and overcome the singular point of the traditional robot with rigid legs. c, d The robot with flexible feet (Fig. 3c) exhibits superiority in obstacle crossing relative to the counterpart with the rigid feet (Fig. 3d). When the robot is exposed to an obstacle (height 160 μm × width 1 mm) on the way forward, it can stride via quick release of the stored elastic energy enabled by the feet deformation. In contrast, the robot decorated with rigid feet is always stuck by the obstacle, irrespective of the direction of the magnetic flux applied