Collective behavior of platelets defines macroscale properties of blood clots

Blood clots are an active biological material in which platelets extend micrometer-long filopodia to impose contractile forces on the fibrin scaffold that lead to drastic macroscopic changes in clot volume and elastic modulus. Blood clots are involved in physiologic and pathologic processes, and blood clotting disorders prevent the body's natural ability to achieve hemostasis and lead to bleeding, stroke or heart attack. Understanding the underlying physics behind the clotting process is essential to developing treatment of these disorders. We develop and experimentally validate a mesoscale computational model to examine the biophysics of clot contraction by directly linking the microscale platelet movements to macroscale blood clot properties and behaviors. We examine how the collective work of platelets contracting surrounding fibrin network determines the clot forces and structure. Furthermore, we probe red blood cell retention during the blood clotting process. Our work provides insights for developing synthetic and hybrid active composite materials with adaptive mechanical property and behavior.