Magnetic Design for the PediaFlow Ventricular Assist Device

Abstract

This article describes a design process for a new pediatric ventricular assist device, the PediaFlow. The pump is embodied in a magnetically levitated turbodynamic design that was developed explicitly based on the requirements for chronic support of infants and small children. The procedure entailed the consideration of multiple pump topologies, from which an axial mixed-flow configuration was chosen for further development. The magnetic design includes permanent-magnet (PM) passive bearings for radial support of the rotor, an actively controlled thrust actuator for axial support, and a brushless direct current (DC) motor for rotation. These components are closely coupled both geometrically and magnetically, and were therefore optimized in parallel, using electromagnetic, rotordynamic models and fluid models, and in consideration of hydrodynamic requirements. Multiple design objectives were considered, including efficiency, size, and margin between critical speeds to operating speed. The former depends upon the radial and yaw stiffnesses of the PM bearings. Analytical expressions for the stiffnesses were derived and verified through finite element analysis (FEA). A toroidally wound motor was designed for high efficiency and minimal additional negative radial stiffness. The design process relies heavily on optimization at the component level and system level. The results of this preliminary design optimization yielded a pump design with an overall stability margin of 15%, based on a pressure rise of 100 mm Hg at 0.5 lpm running at 16,000 rpm.

In Vitro and In Vivo Performance Evaluation of the Second Developmental Version of the PediaFlow Pediatric Ventricular Assist Device

“…Nonetheless, the pump operated stably because of its robust, virtual zero power control. 15 The different motor current, motor speed and estimated flow rates represent the pre-determined set points for each implant.…”

Experimental Study of Micro‐Scale Taylor Vortices Within a Co‐Axial Mixed‐Flow Blood Pump

“…Another conical section at the tail cooperated with stationary blades, wound in the opposite direction, attached to the housing. The dimensions of the cylindrical section are dictated by the integrated motor and magnetic suspension of the prototype pump (4). For the purpose of flow visualization, a transparent housing was constructed with a prismatic shape to avoid distortion because of curvature (see Fig.…”

A Pareto Optimal Design Analysis of Magnetic Thrust Bearings Using Multi-Objective Genetic Algorithms

“…Designs of thrust magnetic bearings for the high load-to-weight ratio and reduced power consumption by using permanent magnets were tested [3,4]. Many practical applications of active magnetic bearings, such as flywheel energy storage systems [5], continuous flow ventricular assist devices [6], Maglev pumps [7], and pedia-flow ventricular assist devices used for pediatric (infant) patients aged below two years [8,9] were implemented in different engineering and medical fields.…”