A micropump including: a stator (4); a rotor (6) slidably and rotatably mounted at least partially in the stator, the rotor comprising a first axial extension (24) having a first diameter (D1) and a second axial extension (26) having a second diameter (D2) greater than the first diameter; a first valve (V1) formed by a first valve seal (18) mounted on the stator around the first axial extension, in conjunction with a first channel (42) in the rotor that is configured to allow liquid communication across the first valve seal when the first valve is in an open position; a second valve (V2) formed by a second valve seal (20) mounted on the stator around the second axial extension, in conjunction with a second channel (44) in the rotor that is configured to allow liquid communication across the second valve seal when the second valve is in an open position; a pump chamber (8) formed between the rotor and stator and between the first valve seal and second valve seal, and a cam system comprising a cam track (22, 22′) on one of the rotor or stator and a cam follower (36, 36′) on the other of the rotor or stator for axially displacing the rotor relative to the stator as a function of the rotation of the rotor, the cam track comprising a valves-closed chamber-full section (28), a valves-closed chamber-empty section (30), an intake section (32) and an expel section (34). The expel section comprises an expel hold position (34b) defining an intermediate axial position between the valves-closed chamber-full section and valves-closed chamber-empty section for partial delivery of a pump cycle volume during the expel phase.