The invention relates to a micromotor (10), the stator of which contains a back iron jacket (18). Said back iron jacket consists of a continuous unslotted sleeve consisting of a metal alloy that contains ferritic iron as the main constituent, up to 30% chromium and preferably aluminium and yttrium oxide. Electric conductivity is reduced by the oxidation of the aluminium. The yttrium oxide performs the same function. The reduced electric conductivity suppresses eddy currents to a great extent. The back iron jacket (18) has a high magnetic conductivity with a small wall thickness, thus increasing the electrical output for a motor with a small diameter.

A blood pump comprises a pump casing having a blood flow inlet and a blood flow outlet connected by a passage, and an impeller arranged in said pump casing so as to be rotatable about an axis of rotation. The impeller is provided with blades sized and shaped for conveying blood along the passage from the blood flow inlet to the blood flow outlet, and is rotatably supported in the pump casing by a first bearing at a first axial end of the impeller and a second bearing axially spaced apart from the first bearing. The first bearing comprises a projection extending along the axis of rotation and connected to one of the impeller and the pump casing and a cavity in the other one of the impeller and the pump casing, the projection comprising an enlarged portion that engages the cavity such that the first bearing and the second bearing are arranged to bear axial forces in the same axial direction.

A blood pump comprises a pump casing having a blood flow inlet and a blood flow outlet connected by a passage, and an impeller rotatable about an axis of rotation. A surface of the impeller faces a surface of the pump casing spaced from said surface of the impeller by a clearance, the clearance being in fluid connection with the passage at a clearance transition point. At least one wash out channel extends through the impeller and is in fluid connection with the passage via a first opening and with the clearance via a second opening. The first opening of the wash out channel is arranged in an area of the impeller that is under a higher pressure than the clearance transition point so as to cause a blood flow from the first opening through the wash out channel and the clearance to the clearance transition point.