  Simulations show that when a phase-separated binary AB fluid is driven to
flow past chemically patterned substrates in a microchannel, the fluid exhibits
unique morphological instabilities. For the pattern studied, these
instabilities give rise to the simultaneous, periodic formation of monodisperse
droplets of A-in-B and B-in-A. The system bifurcates between time-independent
behavior and different types of regular, non-decaying oscillations in the
structural characteristics. The surprisingly complex behavior is observed even
in the absence of hydrodynamic interactions and arises from the interplay
between the fluid flow and patterned substrate, which introduces non-linearity
into the dynamical system.
