Fig. 3. Trapping mechanisms in the heart-shaped structure. Left panels show the design of the heart-shaped reservoir (a) time lapse images of micromotors being trapped in the 40° chevron. A total of 7 micromotors are trapped in ca. 1 min (b) Micromotors swimming towards the center and (c) from the center along the walls of the ratchet mechanism are retained in the trapping chamber. The red, pink and blue arrows on the schematics of the left-side figures indicate the trajectories of the micromotors.