Control of Active Nematics through Friction*

Using continuum simulations, we study the impact of anisotropic friction and of position-dependent friction on the emergent flows of active nematics. We show that, depending on whether the active particles align with or tumble in their collectively self-induced flows, anisotropic friction can result in markedly different patterns of motion. For a flow-aligning system with high anisotropic friction, the otherwise chaotic flows are streamlined into flow lanes, reproducing the experimental laning state, which has been obtained by interfacing microtubule-motor protein mixtures with smectic liquid crystals. However, this state is not possible in the flow-tumbling regime, emphasising the role of the flow-tumbling parameter in the dynamics of active nematics. Furthermore, we show that position-dependent friction in active nematic layers allows for the control of the active flows by creating effective hydrodynamic boundaries. Our work demonstrates novel methods to control active matter without the introduction of invasive solid bounding walls.