The invention concerns a flow regulator, made of a stack of 3 plates, respectively a top plate including a flexible membrane (1), a middle plate (2) with pillars and through holes and a bottom plate ( 3 ) with fluidic ports, micro channels and through holes (8,9,12). The principle is based on the deformation of the membrane due to the pressure of the liquid. The membrane goes in contact with the pillars of the middle plate, obstructing gradually the through holes of the pillars. The device is designed to keep the flow constant in a predefined range of pressure. The device is dedicated to ultra low flow rate up to 1 ml per day or below, typically for drug infusion. Plastic flow regulators comprise preferably several independent valves coupled in parallel. The membrane plate is therefore made of several flexible membranes obstructing gradually the flow by increasing the pressure. Stress limiters are used to avoid plastic deformation of the membrane. For implanted pump, the use of a flow regulator instead of a flow restrictor has several advantages, including the possibility to reduce significantly the reservoir pressure and to generate directly the pressure during the pump filling by using an elastic drug reservoir.