Development of a Blood Shear Stress Device using Numerical and Experimental methods
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Left Ventricular Assist Devices (LVADs) are mechanical pumps used to treat heart failure, which is the cause of 6.2 million deaths in the United States every year. Despite clinical success, the capability of LVADs to operate successfully without causing blood damage remains a challenge. Due to high fluid stresses for prolonged period, the circulatory components of a LVAD tend to cause mechanical destruction of red blood cells leading to the release of hemoglobin into the bloodstream, termed as hemolysis. We have developed a Blood Shear Stress Device (BSSD) for LVAD component testing which will aid in identifying the amount of blood damage caused and its source. This device will enable individual component analysis thereby improving LVAD design while simultaneously reducing development time and cost. The BSSD consists of an active and passive magnetic levitation system for the brushless DC (BLDC) motor and uses a large gap between the BLDC motor components as a blood flow region for the component testing of LVADs. The passive magnetic levitation system is comprised of two concentric permanent magnet bearings used to stabilize the BLDC motor radially. The development process of this device involved magnetic modelling using numerical and experimental methods to identify the dimensions of the BSSD components to eradicate the blood damage caused by the circulatory components. The proposed device design has been evaluated using computational fluid dynamics analysis for the blood damage caused due to the circulatory components of the BSSD by measuring the fluid shear stresses and their exposure time on the blood.