Abstract
Among typical active matter such as self-propelled micro-objects, the characteristic collective motion
originating from the hydrodynamic interaction between constituents has been observed in both biological
and artificial systems. In this study, we report various kinds of autonomous collective motion of
micrometer-sized particles in a one-dimensional driven system by an angular momentum of light. The
regular stationary and dynamic arrangements resembling “crystals” or “clusters” is induced by longranged
hydrodynamic interaction between particles in low Reynolds numbered system. A transition in
the collective motion has been observed by varying the size ratio of the particles in binary-sized systems.
We have also studied the influence of spatial confinement on the collective motion and obtained a
complex motion phase diagram as a function of angular momentum and spatial confinement.
