Fig. 1

Flow states. a Top view of the experimental setup including the relevant spatial dimensions. A polymer plate with rectangular openings is placed, by means of a micropositioner, at the interface between the active fluid and silicon oil, thus constraining the existing active nematic. b–d Confocal fluorescence micrographs of an active nematic interface confined in channels of different widths. Scale bar: 100 μm. e–g Corresponding simulations of the experimental system. Streaking patterns follow the director field tangents. They are produced using a Line Integral Convolution of the director field⁵⁶ with Paraview software.The colour map corresponds to the computed nematic order parameter, q. b, e Correspond to strong confinement, where the filaments are organized into a unstable shear alignment regimee. c, f Illustrate the effects of moderate confinement, forcing a new dynamical regime of the defects. d, g Correspond to the active turbulence regime