Hydrodynamic coupling of spheres
Hedrodynamic interactions (HI) play an important role whenever two or more particles move in a viscous fluid. Due to their long-range nature, they govern the dynamics of colloidal suspensions, e.g. during self- and collective diffusion, sedimentation, and aggregation processes. Here we demonstrate that HI leads to a novel motional behavior of colloidal particles driven by a constant tangential force along a toroidal trap. Owing to HI, we observe an interesting limit cycle, which has been recently predicted by Reichert and Stark. In addition, we demonstrate how the collective motion of interacting particle changes when a sawtooth potential is added to the constant driving force. We demonstrate that in this case the particles exhibit an unexpected caterpillar-like motion, which facilitates the surmounting of potential barriers.