Biphasic Structure-Based Modeling of Tissue Equivalent Mechanics

The collagen gel has been extensively studied as an in vitro model for soft tissue mechanics, cell-ECM interactions, and as a prototypical bioartificial tissue; a model of gel mechanics from a microstructural perspective is important for all of these [1]. An earlier experimental study recorded the microstructural rearrangements during confined compression by interpreting the evolution of birefringence patterns within the gel [2]. The patterns suggested that strain was transmitted by fiber rotation at interconnections and was non-uniform due to fluid permeation resistance, indicating that macroscopic gel mechanics arise from elastic interactions between the solid phase fibers and viscous interactions with fluid. A structure-based mathematical model to account for both the elastic and viscous response of tissue equivalents was developed.