|
Self-propelling active particles, like bacteria or Janus particles, demonstrate
a variety of dynamical patterns ranging from swimming of individual particles to
large-scale synchronised collective motion of a large number of swimmers. A new
type of collective behaviour has recently been observed in dilute solutions of
the bacteria E. coli in the presence of short-range depletion-induced attraction between
the bacteria [1]. When the attraction is strong enough, bacteria form clusters that
simultaneously rotate and translate due to the active nature of individual particles
constituting the clusters. We present a theory based on hydrodynamics to predict
the rotation and translation speed of the clusters as a function of the cluster's size.
The translational velocity is found to be roughly independent of, while the angular
velocity decreases as a function of the cluster's size.
[1] J. Schwarz-Linek et al. in preparation |
|