Tunable rotating active nematic states in the collective motions of self-propelled, chiral filaments.

In gliding assay experiments on microtubules and kinesin motors, microtubules at sufficient density form a long-range-ordered active nematic state whose director rotates counterclockwise. We investigate the emergence of this bulk rotation and its connection to the microtubule structure using Brownian dynamics simulations of self-propelled, semiflexible filaments with chiral activity. We demonstrate that this chiral activity, even in the absence of shape chirality, is sufficient to produce a coherently rotating active nematic director. Our model predicts that the rate of rotation is strongly dependent on the filament bending rigidity: Surprisingly, for a given chiral activity, the rotation can be reversed in handedness or tuned to zero by altering the rigidity. Chiral activity also significantly affects the interplay of polar and nematic symmetries in the long-range-ordered steady state.