Design and Implementation of a Novel Passive Magnetically Levitated Nutation Blood Pump for the Ventricular-Assist Device

Abstract

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.

Levitation Stability of the Passive Magnetic Bearing in a Nutation Blood Pump

“…We confirmed the basic principles for the operation of the nutation blood pump proposed in Ref. 7. In addition, we developed more comprehensive models and performed some real-time test measurements toward solving the problems of levitation stability in a nutation blood pump.…”

“…Past arrangements of permanent magnets usually had a defect of large magneticforce fluctuation of the bearing during rotation. (7) As shown in Fig. 1, there are only two pairs of magnetic rings in the bearing of the current blood pump.…”

“…(3) Several blood pumps with passive magnetic bearings have been developed for use in clinical settings, such as the Valvo pump, (4) HeartWare HVAD, (5) and Arrow CorAide. (6) Furthermore, Chen et al (7) proposed a passive magnetically levitated nutation blood pump with advantages of a small volume rate and low rotational speed. They experimentally verified the structure and principle of blood flow in the pump.…”

Design and Cosimulation of Twelve-Pole Heteropolar Radial Hybrid Magnetic Bearing

“…where R m is the permanent magnet reluctance, μ m is the permeability of permanent magnetic materials, and S m is the area of the stator pole. e bias flux in the branches produced by the permanent magnet is defined as ϕ k (k � 1, 2, 3,4,5,6,7,8,9,10,11,12). erefore, the bias flux of each branch can be calculated by…”

“…Based on the above characteristics, HMB has irreplaceable advantages in the field of small size and low power consumption. Hence, HMB has broad application prospects in many industrial occasions such as flywheel energy storage system (FESS) [6], artificial heart [7], high-speed blower [8], molecular vacuum pump [9], and so on [10].…”