Magnetically actuated heart assist pump

Abstract

Magnetic actuation, requiring no moving, mechanical parts, as a direct magnetic-to-hydraulic energy conversion system for producing pulsatile pumping for a left ventricular assist device (LVAD), was investigated and proven. An axi-symmetric, ellipsoidal pump was built using the three magnetic actuators mounted 120° around the ellipsoidal bladder. Each actuator consists of a variable rate dc-pulsed electromagnet opposite a like polarity rare-earth cobalt permanent magnet attached to the bladder. The ellipsoidal pump geometry imposed two severe design constraints: magnetic force vector alignment and limitation of effective area available for magnetic pumping force application. Efforts to increase the flux density of the electromagnet led to the development of several advanced passive techniques for flux enhancement, e.g., use of smaller permanent magnets critically located in the electromagnet core, shaped core geometry, and flux shell geometry. These have virtually doubled dynamic flux density to values exceeding 0.8 web/m <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> , with no additional power consumption. Preliminary data indicate that shaped, hollow cores, such as prolate spheroids, providing core weight reductions to 60% will enable in excess of 95% solid core flux.