Interactions between comoving magnetic microswimmers

The artificial microswimmer [R. Dreyfus et al., Nature (London) 437, 862 (2005)] whose mechanism of propulsion is the magnetically driven undulation of a flagellum-like tail composed of chemically linked paramagnetic beads can be used as a physical model with which to study low-Reynolds-number swimming. Understanding how such swimmers interact provides insight into the related problem of quantifying the hydrodynamic interactions between microorganisms. In this study, particle-based numerical simulations are conducted of two comoving artificial swimmers. The resulting swimming speeds are determined over a range of separations for swimmers driven by planar and rotational magnetic fields. The far-field hydrodynamic interactions are analyzed and found to decay as h(-2) where h is the separation distance. Additionally, the role of the interswimmer magnetic forces is determined.