NOVELTY - A passive membrane valve for use with a microfluidic pump, comprises a valve membrane sheet (160, 230) comprising an opening region and a valve seating region. The valve membrane sheet confines transport of fluid from the inlet channel to the outlet channel where fluid may be purged. It comprises a passive mechanism for restricting backflow of purged fluid back into the inlet channel.    USE - The invention is for use with a microfluidic pump, useful for a microfluidic pumping system, or a multilayer micropump device (claimed) for microfluidic applications. It is for use in any fluid transport system. It is useful for fuel cell fuel delivery and/or partitioning applications.    ADVANTAGE - The invention achieves improved performance and efficiency. It achieves improved process control and manufacturing at lower cost.    DETAILED DESCRIPTION - A passive membrane valve for use with a microfluidic pump, comprises a valve membrane sheet comprising an opening region and a valve seating region; an inlet channel adapted to receive fluid for transport across the valve membrane sheet; and an outlet channel. The valve membrane sheet confines transport of fluid from the inlet channel to the outlet channel where fluid may be purged. It comprises a passive mechanism for restricting backflow of purged fluid back into the inlet channel, where the valve-seating region seats against a sealing component.    INDEPENDENT CLAIMS are also included for:    (a) a microfluidic pumping system comprising a passive membrane valve, and a pump actuator and/or a piezoelectric actuator (220);    (b) a multilayer micropump device comprising a substrate (100), passive membrane valve, a pump actuator, and a pumping cavity; and    (c) a method of fabricating the multilayer micropump device comprising providing substrate layers; forming into substrate layers a transport conduit and a cavity, the transport conduit and cavity in microfluidic communication to define a fluid transport path and a pumping cavity respectively; placing within the fluid transport path a passive membrane valve; and laminating each of the substrate layers to form a monolithic micropump device.    DESCRIPTION OF DRAWING(S) - The figure representatively illustrates a cross-section, elevation view of a micropump device package, during an intake stroke.    Substrate (100)    Valve membrane sheet (160, 230)    Seating mechanism (170)    Piezoelectric actuator (220)