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Considering the wear in mechanical bearings and the requirement for sensors or electrical power in active magnetic bearings, a novel nutation blood pump using a passive magnetic spherical bearing was developed in this paper. A mathematical model was derived to calculate the magnetic forces of the bearing between two pairs of magnetic sleeves in the nutation process. The calculation results demonstrate that the fluctuations of magnetic forces enlarge with the increase in the nutation angle; the magnetic forces obviously increase with the decrease in the air gap, especially along the z-axis. The dynamic magnetic finite element simulation was carried out to validate the mathematical model. The simulation and calculation results of the magnetic forces show consistent trends and provide a theoretical basis for the parameter design. To validate the performance of the pump, computational fluid dynamics (CFD) analyses and in vitro experiments were conducted. The predicted values of the flow velocity vector through the pump, and the wall shear stress, demonstrate that the pump has an antithrombotic property and would not cause serious blood damage. The hydraulic experiment shows that a pressure rise can be achieved in the range of 60-140 mmHg, at a rotational speed of 600-1600 rpm and a flow rate of 0.4-6.7 L/min. The normalized index of hemolysis (NIH) of the nutation pump was 0.0043 ± 0.0008 g/100L. The in vitro tests indicate the feasibility of a magnetically levitated ventricular-assist nutation blood pump for further suspension stability and animal trials.

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Rotor stability is an important index of the performance of a magnetically levitated blood pump. In this study, we developed a novel nutation blood pump using a passive magnetic spherical bearing to achieve dynamic stability of a levitated rotor. The structure and working principle of the proposed blood pump are first introduced. A mathematical model based on the theory of equivalent magnetic charges is derived to calculate the axial and rotational stiffnesses of the passive magnetic spherical bearing. Furthermore, considering the gyro effect on the dynamic stability, an analytical expression for the gyroscopic moment of the nutating rotor is deduced. Finally, a prototype of a self-designed blood pump is fabricated, and a hydraulic experiment on the real-time levitation state is carried out. Experimental results obtained via different sensing components show that a continuous output flow rate of 5 L/min can be obtained against a pressure head of 100 mmHg at a rotational speed of 1600 rpm, and the output flow conditions are found to be stable at various pressures. In addition, it is found that the rotor becomes more stable with increasing rotational speed. The maximum fluctuation of the levitated gap is only 0.2 mm when the rotational speed of the rotor is 2300 rpm.

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