Interplay of Driven Flow and Active Stress in Tumbling Nematic Liquids

Active liquid crystals (LCs) are a paradigm of active matter in which topological defects can constantly nucleate and annihilate, accompanied by a spontaneous flow. It has invoked recent interests thanks to its potential applications in microfluidics and close connections to certain biological systems. One experimental system of active LCs is bacteria swimming in a nontoxic, lyotropic chromonic liquid crystal. Recent works have revealed its tumbling character and low twist modulus. However, how these unique features modify the fluid dynamics of an active nematic in the presence of an external flow is poorly understood, hindering its applications in microfluidics. Here, we use hydrodynamic simulations to address this question. We find that the direction of the spontaneous flow developed in a flow-tumbling active nematic is tunable by tuning the active stress. We further show that for a flow-tumbling nematic subject to a pressure-driven flow, activity can suppress the flow rate in a planar-anchoring cell but promote a director field transition in a homeotropic-anchoring cell. We also predict a pattern formation in an unsteady flow of a flow-tumbling active nematic. As such, our results pave the way towards microfluidic applications of tumbling active nematics.