Numerical Modelling of Red Blood Cell Structural Mechanics

Red blood cells (RBCs) are the most abundant cellular elements in blood and their main function is the oxygen delivery. Structurally RBCs are highly deformable membrane-bounded liquid-core capsules. The deformability is critical to fulfill the functionality and is greatly affected by the RBC structural mechanics. Due to the small size, in vivo/vitro studies of the RBCs are often impossible where, being an alternative, numerical modellings stand out to be a robust approach to investigate the the RBC. In the recent years the spring-particle-based (SP) RBC modelling becomes very popular due to the simplicity and extensive modelling capability over the conventional approach using the continuum mechanics. The SP-RBC models use closed spring networks representing the membrane and the enclosed volume for the liquid core. Despite a number of successful applications, the modelling suitability still is questioned. In addition since the development of the SP-RBC model, the spring network employed is typically pre-stressed and results into inaccurate estimation of the membrane mechanical properties. Also the membrane bending is calculated based on the angle between the neighbouring triangle elements of the network and results in incapable of modelling complex membrane geometry. In light of these observations an enhanced SP-RBC model is proposed. In this model a stress-free spring element is used to comprise the network and the bending is calculated based on the membrane curvature. Through three replications of the experiment tests, i.e. optical tweezers test, vesicle transformation, and the stomatocyte-discocyte-echinocyte transformation, the accuracy and capability of the enhanced SP-RBC model is justified