Active nematic pumps in microfluidic systems

Active fluids can power microscale flows without external energy input, but their intrinsic turbulence limits controlled transport. Combining experiments and simulations, we show that embedding triangular posts in an active nematic film transforms chaotic dynamics into directed, self-sustained flows. Acting as active boundary layers, the obstacles continuously inject topological defects that reorganize local velocity fields into vortex lattices and break fore-aft symmetry. This process yields stable pumping structures that drive cargo transport and mixing without rigid walls or pressure sources. We quantify the performance of these autonomous pumps, individually and in arrays, by analyzing output velocities and pressure buildup. Finally, we demonstrate that tuning obstacle geometry enables precise control of active flow architectures, opening routes toward defect-mediated, self-powered microfluidic systems.