A theoretical framework to determine the optimal centrifugation angle for separation of plasma from blood samples

The separation of blood plasma by centrifugation can be accelerated by placement of the sample at an angle relative to the direction of the centrifugal force. This geometric effect, which has been known for a century, is due to the Boycott effect, while the enhanced sedimentation of red blood cells (RBCs) in tilted vessels can be attributed to buoyancy-induced convection. Moreover, flow instability would invalidate the traditional predictive model and weaken separation enhancement. While current model considers only the geometric effect, by considering the buoyancy-induced convection and flow instability, we devise a model for the first time enabling the prediction of the optimal tilt angle to achieve the highest separation efficiency. A comparison of our theoretical prediction with the available experimental data shows good agreement. A sensitivity analysis is also conducted to investigate the influence of variation in blood samples on the physical parameters.