The Thin Maglev Ventricular Assist Device with Radial Type Self-Bearing Motor

A small, thin, maglev ventricular assist device, which can be implanted under the thorax muscle layer like a pacemaker, has been developed. A cascade pump, which has inlet and outlet ports in the same plane and a radial type self - bearing motor are adopted to reduce the axial thickness of the device. The radial self - bearing motor is using the passive stability to restrict the impeller movement in the axial direction and its inclination. We evaluated the fluid force acted on the levitated impeller by using the computational fluid dynamics analysis and restoring force and torque by using the magnetic field analysis. Also, an axial hydrodynamic bearing is developed to avoid the impeller contact on the casing when the levitated impeller received a large disturbance. Finally, a prototype pump is developed and evaluated its levitation and pump performance. The prototype pump was levitated and rotated up to a rotating speed of 2,600 rpm successfully. The target performance of a flow rate of 2 L /min against a head pressure of 100 mmHg is achieved with a rotating speed of 2,000 rpm. The maximum oscillation amplitude and the total power consumption with the target performance were 17 µm and 4.5 watts.