# A Review of Innovative Electromagnetic Technologies for a Totally Artificial Heart
## 5 Unconventional Electromagnetic Actuators
### Contactless Power Transfer (CPT)  
Two approaches are proposed for this kind of actuators. The first one relies on external moving PMs, driven by a conventional rotary electric motor, magnetically interacting with inner PMs to produce a pumping function without using any winding. The absence of copper losses significantly limits thermal issues related to both the power transfer and the actuator operation. Other benefits are the very compact assembly, particularly profitable, for instance, for pediatric application, the ease of setting and tuning of the main drive control, and the low risk of infection transmission. In Figure 12a, a rotating motor supplied by a separate source (i.e., external battery pack) drives a disk-type version of the actuator with an external 2-pole ring-shaped PM rotor [80]. During rotation, the axially magnetized PMs alternately repel and attract the inner 2-pole PM ring, constrained to a linear reciprocating motion by mechanical coupling to a spline shaft. A diaphragm, which separates the blood flow from the oscillation chamber, prevents any contamination and hemolysis problems. The reinforcement of the air-gap flux density by an iron yoke and a proper selection of the diameter of the disk hole yields peak values of the attractive and repulsive force at least of 55 N and 15 N, respectively, with a minimum air-gap length (skin thickness included) and a disk outer diameter of 10 mm and 63 mm, respectively. Instead of rotating, in normal operations the prime motor swings through a 180\({}^{\circ}\) angle. The maximum output pump power is 0.65 W at an average speed of 92 rpm with a blood flow of 81/min. The total pumping efficiency is 32%, appreciably higher than other conventionally motor-driven TAHs. The same principle applies by replacing the axial flux configuration with a radial flux one, where the rotating magnetic field generated by an external stator primary poly-phase winding interacts with an implanted cylindrical PM rotor. Figure 12b describes a two-phase winding arrangement in [81]. The effective interaction area is limited by the chest curvature; moreover, flux leakages are relevant because of the absence of back iron. However, no shaft or mechanical bearings are required, and the pump impeller can be integrated with the rotor without any mechanical coupling. The pump sized for pediatric VAD was successfully tested in animals that produced an average flow rate of 1.5 1/min at 50 Hz (3000 rpm) with  
Figure 12: Configurations for the contactless mechanical power transfer; (**a**) external rotating PM disk coupled with an implanted reciprocating PM disk; and (**b**) external 2-phase coils supplied by 90\({}^{\circ}\) shifted sinusoidal currents interacting with a 2-pole PM rotor. a 2-3 cm distance between the pump and the driving coil. Pump efficiency is approximately 20 to 40% at the average flow rate (1.7 to 2.0 l/min), with a speed ranging from 3000 rpm (50 Hz) to 6000 rpm (100 Hz). An alternative to the configuration of Figure 12a could consist of a linear-to-linear motion transmission using external and implanted rectified PM arrays [82]. Such a configuration corresponds to a magnetic coupler, where the inner PM array is driven by the motion of the outer one. Such an arrangement is claimed to be immune to the shortcomings due to fatigue in the flexible blood pockets of most state-of-the-art bionic pneumatic or electric blood pumps. The outer active PM array is driven by a linear motor or by a rotary motor coupled to a rotary-linear motion converter. The piston enclosed in the pump casing holds the passive magnet; the casing is provided with openings on both ends connected to the aorta and the vein, respectively. A one-way valve allows blood flow from the chamber connected to the aorta to the vein, reproducing diastole in the natural heart. Simulations with NdFeB hexahedral 2-pole PMs (sizes: 30 mm \(\times\) 20 mm) distanced by 60 mm evidence the feasibility of the configuration, providing 1.2 W at 70 ppm.