Active Turbulence in Quasi-Two-Dimensional Living Liquid Crystals

Living liquid crystal is an intriguing far-from-equilibrium system composed of swimming bacteria in a lyotropic liquid crystal. Advances have been made in understanding and controlling bacterial collective motion via topological defects. Here, we study turbulent motion behavior of living liquid crystals confined in quasi-two-dimensional thin films, where the boundary sets a planar anchoring for the liquid crystals. We report a wealth of interesting observations, including exponential probability distribution for bacterial velocity, coupling between the active turbulence and long-range orientational order of the medium, creation and annihilation of topological defects at different bacterial concentrations. We will discuss the physical mechanisms behind these observations.