DEVELOPMENT OF AN AXIAL FLOW BLOOD PUMP WITH HYDRODYNAMIC CONICAL BEARINGS

Abstract

Levitating an impeller such as a magnetic suspension is required for long-term implantable rotary blood pumps. However, magnetic suspension requires some complicated controls or sensing modules. The main purpose of this study is to develop an implantable axial flow blood pump that enables the impeller to be levitated using only a hydrodynamic bearing. The rotor, which was designed in the shape of a spindle to levitate and rotate the impeller, consists of an enclosed-impeller, permanent magnets for rotation, and two hydrodynamic conical bearings with spiral grooves, which are placed over the enclosed-impeller. The spindle rotor is passively suspended in the axial and radial directions at the same time by rotation. The conical bearing that was built in the spindle rotor was demonstrated to levitate by basic experiment. The hydraulic performance was examined by using a mock circulation. A prototype pump consists of a flow straightener, a diffuser, the spindle rotor with the enclosed-impeller, and a stator of a brushless DC motor. The diameter and height of the enclosed-impeller are 12 and 65 mm, respectively. An in vitro test demonstrated a 6 L/min maximum flow rate and 223 mmHg maximum pressure head at a pump speed of 12,000 rpm. The flow rate of 5 L/min at 100 mmHg pressure head was achieved at a pump speed of 12,000 rpm. Therefore, the axial flow blood pump with hydrodynamic conical bearings would be expected to be applicable for implantable rotary blood pumps.