Figure 4.

Flagellar-based propulsion mechanisms. (A) Rotation of bacterial flagellum at frequency ω₁ through rotary motor inside and a counter-rotation of the head at frequency ω₂, while head and tail of ABF rotate in the same direction. (B) Typical types of magnetic ABFs. Reproduced with permission from ref (149). Copyright 2018 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim. (C) Field frequency-dependent ABF movement: ABF wobbles with a wobbling angle at low frequency; wobbling movement transforms into corkscrew-like swimming; then the wobbling decreases to zero at high rotational frequencies. Example of frequency-dependent propulsion of MOF-based helical swimmers. Reproduced with permission from ref (155). Copyright 2019 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim.