2.6. Gait type

To analyze the locomotion characteristics of MR-DF and MR-LF, the gait type for the first ten steps (five seconds) of each experiment trial was identified and organized in the table in Figure \ref{490314}A. Gait was classified into five categories: run, walk, crawl, no travel, and inhibited (images during one step of the run, walk, and crawl gaits are shown in Figure \ref{490314}B). In the “run” gait, both robot feet were simultaneously off the ground at some instances during locomotion; in the “walk” gait, only one foot was off the ground at a time; and in the “crawl” gait, both feet stayed in contact with the ground. If the robot was unable to move more than 10 mm during the 60-second test and remained in contact with the bottom of the lumen, the gait is defined as “no travel.” If the robot was lifted and unable to move due to the lifting forces of the actuator magnet, the gait is defined as “inhibited.” We reported the gait type exhibited during a majority of the first ten steps as, in some cases, the differences between gait types could be subtle. We reported a combination of gait types in cases (e.g., during transition) where the robot exhibited an approximately equal ratio of two gait types.