Beyond Bulk Rheology: The Hidden Mechanical Microenvironment of Blood

Abstract: Blood is a dense suspension of deformable cells. While its bulk rheology has been studied extensively, much less is known about the mechanical environment experienced by individual cells and molecules. In concentrated blood, red blood cells (RBCs) continuously interact and rearrange, generating strong fluctuations in local velocity and stress. I will first show how these collective RBC dynamics govern transport. Multiscale simulations reveal anomalous shear-induced diffusion of suspended particles that is strongly anisotropic and depends nonlinearly on shear rate and hematocrit, demonstrating behavior that cannot be explained by bulk flow alone. I will then show that the same microscale fluctuations can regulate molecular mechanobiology. Our simulations predict that concentrated RBC suspensions amplify tensile forces on von Willebrand factor (VWF), while our experiments show corresponding changes in VWF cleavage, platelet aggregation, and thrombotic occlusion. Finally, I will introduce our ongoing efforts to combine imaging, computational mechanics, and physics-informed machine learning to infer these microscale rheological fields that are otherwise inaccessible. Together, these studies suggest that blood creates a dynamic mechanical microenvironment that governs transport, molecular function, and hemostasis beyond what can be understood from bulk rheology alone.

Biography: Dr. Leo Liu is a tenure-track assistant professor in the Department of Chemical and Biomedical Engineering at the FAMU-FSU College of Engineering. Before joining the department in Fall 2022, he was a postdoctoral fellow in the Division of Applied Mathematics at Brown University supervised by George Em Karniadakis. He received his Ph.D. in Mechanical Engineering from Georgia Tech in 2021, where he was advised by David N Ku and Cyrus K Aidun. His research group integrates advanced computational modelling and lab-on-a-chip techniques to study blood as a concentrated suspension and to understand how its biorheology relates to heart attacks, strokes, and severe bleeding. He currently serves as Co-Chair of the Biorheology Subcommittee of the International Society on Thrombosis and Hemostasis (ISTH). His research has been recognized with awards including the FSU First-Year Assistant Professor Award (2023), Eberhard F. Mammen Young Investigator Award (2024) and the inaugural Shmuel Einav Award for Mechanobiology (2025).