This invention describes an intermediate pump that can be placed between two microreactors to control the flow rate and/or pressure of fluid between them. The pump comprises two fluid enclosures which provide two parallel flow paths between the pump inlet and outlet. When the pump is used to transport a liquid payload, each of the two enclosures is partially filled by the payload fluid. During operation, a gaseous pressurizing fluid is introduced into the headspace above the payload to increase the pressure in a particular enclosure, thereby driving the flow of payload through the outlet. Subsequently, the flow of pressurizing fluid is redirected into the other enclosure while payload fluid continues to flow under residual pressure. By careful control of the flow of pressurizing fluid, the net flow rate from across the pump (i.e., the sum of flow rates through each of the two enclosures) can be maintained at a constant level, enabling non-fluctuating flow.The pump can be constructed at the macroscopic scale using glassware or microfabricated from silicon, enabling a wide range of flow rates ranging from nanoliters to milliliters per second to be achieved. Additionally, the use of inert construction materials allows the pump to be used to transport a wide range of fluids, including harsh chemistries that degrade exiting elastomer-based microfabricated pumps.