We report the utility of structured elastomeric membranes (SEMs) as a multifunctional microfluidic tool. These structured membranes are part of a two-layer microfluidic device, analogous to membrane valves, with the novelty that they incorporate topographical features on the roof of the fluid channel. We demonstrate that when the topographical features are recessed into the roof of the fluid channel, actuation of the membrane leads to effective confinement of fluids down to femtolitres in preformed microfluidic containers. Thus, the SEMs in this case function as fluidic traps that could be coupled to microfluidic networks for rapid and repeated flushing of solvents. Alternatively, when the topographical features on the roof protrude into the fluid channel, we demonstrate that the SEMs can be used to pattern proteins and cells in microchannels. Thus in this case, the SEMs serve as fluidic stamps for functionalizing microchannel surfaces. In addition, we show that the trap or pattern shape and size can be manipulated simply by varying the topography on the elastomeric membrane. Since SEMs, membrane valves and pumps use similar fabrication technology, we believe that SEMs can be integrated into microfluidic large-scale circuits for biotechnological applications.