Modeling and Characterization of Artificial Bacteria Flagella with Micro-structured Soft-magnetic Teeth

Sub-structures such as micro-structured magnetic teeth fabricated with an artificial bacteria flagellum (ABF) are designed for achieving more motion modes, higher precision, and better controllability. To achieve these, a more precise model considering the non-circular cross-sectional features is setup without simplifying the structure as a helical filament with a circular cross-section as having been used in previous investigations, making it possible to include the effects of the substructures into the motion equation. Analyses and experiments verified the correctness. Besides of the geometric effects, our experimental observation also shows an anomalous step-out frequency appeared in an ABF. This asynchronous motion is attributed to the lag of magnetization with respect to the external rotating magnetic field due to the geometries and the soft-magnetic materials of the ribbons, which is different from the regular asynchronous motion solely caused by low Reynolds number of fluid to microscopic swimmers. While the lag of magnetization can be further attributed initiatively to the soft magnetic materials adopted, the feasibility to arrange the easy axis will enable many new possibilities, which is of particular interest in generating more modes for swarms such as cascade stepping out of ABFs with the same nominal overall sizes and for more precise positioning using stepping motion.