Characterizing the swimming properties of artificial bacterial flagella.

Artificial bacterial flagella (ABFs) consist of helical tails resembling natural flagella fabricated by the self-scrolling of helical nanobelts and soft-magnetic heads composed of Cr/Ni/Au stacked thin films. ABFs are controlled wirelessly using a low-strength rotating magnetic field. Self-propelled devices such as these are of interest for in vitro and in vivo biomedical applications. Swimming tests of ABFs show a linear relationship between the frequency of the applied field and the translational velocity when the frequency is lower than the step-out frequency of the ABF. Moreover, the influences of head size on swimming velocity and the lateral drift of an ABF near a solid boundary are investigated. An experimental method to estimate the propulsion matrix of a helical swimmer under a light microscope is developed. Finally, swarm-like behavior of multiple ABFs controlled as a single entity is demonstrated.