Impact of gap size and groove design of hydrodynamic bearing on plasma skimming effect for use in rotary blood pump

Spiral groove bearing design for improving plasma skimming in rotary blood pumps

High-efficiency plasma skimming is hopeful to prevent hemolysis inside spiral groove bearings (SGBs) because it can exclude red blood cells from the ridge gap with a high shear force. However, no study reveals the shape design of SGBs to improve plasma skimming. Therefore, this study proposed and applied a groove design strategy to designing an optimal SGB for enhancing plasma skimming in a rotary blood pump (RBP). Initially, we proposed the design strategy that the shape of the groove for enhancing plasma skimming corresponds to the direction of blood flow in the ridge gap. Second, we visualized the cell flow in a specially designed experimental RBP to determine the direction of blood flow, which was helpful in the subsequent SGB design. Then, we created an SGB to provide superior plasma skimming and applied it to the experimental RBP. We evaluated the plasma skimming effect of SGB at rotational speeds ranging from 2400 to 3000 rpm and hematocrit conditions between 1% and 40%. At a 1% hematocrit, the plasma skimming efficiency for the entire SGB was greater than 95%. In all hematocrit conditions, the efficiency at the inner ridges of the SGB was greater than 80%. The results showed the designed SGB successfully induced excellent plasma skimming within ridge gaps. This study is the first to propose and apply a shape design strategy to generate excellent plasma skimming within an SGB. This study may contribute to the prevention of SGB hemolysis inside SGB for use in RBPs.

Hydrodynamic Performance of an Optimized Spiral Groove Bearing to Improve Plasma Skimming Effect

Plasma skimming in spiral groove bearings (SGBs) has the potential to reduce hemolysis by guiding the red blood cells to escape from the narrow ridge gap with high shear stress force, to the larger groove gap. In our previous study, we designed an optimal SGB-PS that aims to improve plasma skimming inside the bearing gaps and verified its effectiveness under whole blood conditions up to 40% hematocrit level. This study extends our work by evaluating the load-carrying capacity of the optimized SGB design. We first analyzed the load-carrying capacity numerically by calculating the hydrodynamic force based on the Reynolds equation. Then we designed and manufactured an experimental device to measure the generated hydrodynamic force under comparable conditions. Our results indicate that the hydrodynamic force generated by the SGB-PS meets the requirements for our hydrodynamically levitated rotary blood pump and aligns well with our numerical analysis. This research contributes to improving the performance of the SGB for hemolysis resistance in hydrodynamically levitated rotary blood pumps.