Oral: Poroelasticity and permeability of fibrin and collagen hydrogels

Biopolymer networks, the backbone of intra- and extra-cellular structures, experience constant, dynamic, mechanical forces in vivo. Understanding their mechanics and permeability characteristics is crucial for elucidating mass transport phenomena and their impact on cell behavior and fibrous structures such as blood clots and solid tumors. Current models that describe permeability cannot explain the nonlinear responses to large mechanical stresses. Conventional experimental techniques face challenges in accurately evaluating the permeability of these networks, hindering comprehensive understanding of their poromechanical behavior. We employ novel experimental approaches and new theoretical models to study these parameters. Namely, by combining rheometer-based compression rheology with camera-facilitated sample shape detection, we directly measure fluid flux and network permeability under controlled compressive strains. By utilizing a piezoelectric motor-controlled stage on a confocal microscope, we explore microscale flow characteristics as well as non-uniform densification of collagen and fibrin hydrogels under compression. With the use of a custom compression geometry, we study fluid pressure distribution on the surface of these hydrogels. Accompanying experimental investigations, finite element and analytical models were developed that align well with the experimental data.