# A Review of Innovative Electromagnetic Technologies for a Totally Artificial Heart
## 2 Main TAH Projects
The first project to implement such technologies was the AbioCor TAH; the internal components consist of [17]:  
* The Li-ion battery (discharge time \(\approx\) 20 min);
* The controller that monitors all the implant components and transmits device performance data using radio frequency telemetry;
* The TET coil that receives high-frequency power that is transmitted across the skin from the external TET coil to recharge the internal battery;
* The electromechanical converter that includes a high-efficiency, high-speed centrifugal pump driven by an electric motor; it adjusts the speed according to the different resistances requested to emulate the systolic and diastolic phases;
* A switching valve used to alternate the direction of the hydraulic flow between the left and right pumping chambers. Even a Japanese project developed an electrohydraulic total artificial heart (EHTAH) system using a TET, a transcutaneous optical telemetry system (TOTS) and an internal battery, which supplies the system for 40 minutes/day [28]. The blood pump actuator is composed of a diaphragm-type blood pump, consisting of a blood chamber and an oil chamber, and a reciprocating electrohydraulic actuator that creates the oil pressure used to drive the diaphragm at alternating intervals. In a revised version, the blood pump and the actuator are connected directly without going through the oil conduit by virtue of the miniaturization of the actuator and the blood pump. Despite the significant volume reduction (500 ml), the pump unit mass was approximately 2.5 kg. Figure 1b shows the integration of the electromagnetic actuator as a replacement for the fluid pump in an electromechanical (EM) TAH [13]. It exerts a push-pull action on the plates  
applied to the membrane separating two blood chambers. The linear oscillating motion is accomplished by converting the motor torque using a rotating to linear motion conversion (e.g., by a lead screw transmission) or by a linear electromagnetic actuator directly coupled to the plates. The latter solution would enhance the system reliability and efficiency, even if it requires high force density actuators. As an example, the ReinHeart project [29; 30; 31; 32] proposes a linear oscillating actuator (LOA) that integrates two movers acting separately on each ventricle. A similar approach is adopted in a project under development at the University of Padova [33; 34]. Innovative bioengineered tissues are tested to exert the pumping action of artificial ventricular membranes, separating electromagnetic LOA from blood flow at the same time. This solution prevents blood contamination and overcomes mechanical wear and reliability issues related to the rotary to linear motion conversion and likely to the presence of springs and of other auxiliary mechanical devices. The development of more compact and unconventional magnetic configuration (e.g., axial type) enabled the conceiving of novel configurations, easing the pump integration, and enabling bearingless arrangements. As an example, the continuous-flow (CF) TAH (Figure 1c) is based on two separate blood pumps acting as a biventricular-assisted device [13]. A single or double electric motor directly drives the pumps. It operates through a continuous rotating motion in one direction without requiring valves or additional hydraulic chambers. Devices adopting this principle mock the natural heartbeat by using different speed values managed by the motor controller. The BiVACOR project represents a typical implementation of such an arrangement [35; 36; 37]. A single axial-flux motor drives the left and right impeller blades of a centrifugal pump, using actively controlled axial magnetic bearings. The axial position of the rotor is adjusted by the signal provided by suitable sensors to control blood flow in the left and right pump vanes.