Development of an implantable motor-driven assist pump system

A motor-driven artificial pump and its transcutaneous energy transmission (TET) system are discussed. The artificial pump consists of a high-speed DC brushless motor driving a ball screw and magnetic coupling mechanism between the blood pump and ball screw. The ball screw transfers high-speed rotary motion into low-speed rectilinear motion by a single component. Magnetic coupling enables active blood filling without applying an excess negative pressure to the pump. The transcutaneous transformer is formed from a pair of concave/convex ferrite cores. This design minimizes lateral motion of the external core. Information on motor voltage is transmitted through the skin by infrared pulses. The motor voltage is regulated by controlling the duty ratio of the square pulse supplied to the primary coil. Pump flow of 5.6 l/min was obtained with a mean outlet pressure of 100 mm Hg at a drive rate of 100 b.p.m. under preload of 15 mm Hg.