a micropump comprising a pumping chamber , an inlet channel communicating with the pumping chamber by an inlet valve and an outlet channel communicating with the pumping chamber via an outlet valve , these elements being manufactured by etching a silicon wafer is then sealed to glass wafers , the micropump also comprising a piezoelectric wafer to vary the volume of the pumping chamber by bending a wall forming part of the wall of this pumping chamber . in accordance with the invention the pumping chamber has a stop which determines the amplitude of movement of the flexible wall . the variation in the volume of the chamber caused by the displacement of the flexible wall is precisely defined , thus making it possible to maintain the output of the micropump constant during normal operating conditions .