Abstract

The initiation of blood coagulation is a critical process in hemostasis and thrombosis, fundamentally dependent on the assembly of coagulation factor complexes on procoagulant surfaces. This study investigates the specific role of **immobilized phospholipids** in providing this catalytic surface, particularly under **flow conditions** that mimic the physiological environment of blood vessels. Using a microfluidic system and surface-immobilized phosphatidylserine (PS) and phosphatidylethanolamine (PE) liposomes, we analyzed the kinetics of the tenase and prothrombinase complexes. Our results demonstrate that the immobilization of phospholipids significantly enhances the rate of thrombin generation compared to free liposomes, suggesting that surface confinement is a key factor in optimizing factor assembly. Furthermore, the application of shear stress (flow) was found to modulate the spatial organization and accessibility of the phospholipid surface, leading to a non-linear relationship between flow rate and coagulation efficiency. These findings highlight the biophysical mechanisms by which endothelial damage and subsequent exposure of immobilized phospholipids contribute to the localized and rapid onset of coagulation, offering new insights for the development of targeted antithrombotic therapies.