  Coupling between flows and material properties imbues rheological matter with
its wide-ranging applicability, hence the excitement for harnessing the
rheology of active fluids for which internal structure and continuous energy
injection lead to spontaneous flows and complex, out-of-equilibrium dynamics.
We propose and demonstrate a convenient, highly tuneable method for controlling
flow, topology and composition within active films. Our approach establishes
rheological coupling via the indirect presence of fully submersed
micropatterned structures within a thin, underlying oil layer. Simulations
reveal that micropatterned structures produce effective virtual boundaries
within the superjacent active nematic film due to differences in viscous
dissipation as a function of depth. This accessible method of applying
position-dependent, effective dissipation to the active films presents a
non-intrusive pathway for engineering active microfluidic systems.
