At these sizes (each quadruped is 20 mm long, with a hip height of 5.6 mm and weight of about 1.6 gram), traditional motors and batteries aren’t going to cut it. Instead, the robot is magnetically actuated, using an externally generated magnetic field. Each of the robot’s four hips has a 2-mm neodymium cube magnet embedded into it, and when you rotate a big magnet in close proximity to the robot, the magnetic field causes those little magnets to rotate as well, spinning the robot’s legs. By changing the dipole orientation of the leg magnets in different combinations, you can cause the robot to move with different gaits, including trotting, waddling, bounding, and pronking:
