Orientational order in confined systems of self-driven spinners

Hydrodynamic interactions play a critical role in the collective behavior of active matter. Here, we investigate large systems of self-driven spinners confined over a substrate. Direct numerical simulation of three-dimensional hydrodynamics demonstrates that these systems generate unique flows from which spatial and orientational order emerges. We show that a transition in particle orientation accompanies the appearance of crystallinity as the packing fraction is increased. Further exploration reveals a rich, tunable state space, offering insights into the biophysics of natural microswimmers with rotational motion as well as into the design of synthetic spinner systems.