Antonino Favata - Univ. la Sapienza (Roma)

Remodeling, plasticity, memory effects in fibrous materials: how cancer devises strategies to outsmart us

Fibrous materials may undergo a plastic internal reorganization, which turns out in the emergence of preferential directions. This is a peculiar behavior of many biological tissues, which drive reorientation by external stimuli at chemo-mechanical levels. In particular, it is detected that contractile cells can reorganize fibrous extracellular matrices and form dense tracts of aligned fibers (fingers), that guide the development of tubular tissue structures and may provide paths for the invasion of cancer cells. 

In the initial state, the fiber network exhibits complete randomness, resulting in a homogeneous material. However, upon loading, certain fibers undergo buckling, leading to a loss of stiffness in specific directions and the emergence of transverse anisotropy. When the applied forces are removed, the strength of these fibers can partially recover, but the material retains a memory of its past history.

I will present a simple mechanical model that describes the fundamental aspects of the aforementioned phenomena: (i) the emergence of the anisotropy, by means of a macroscopic measure of the stiffness of fibers in the direction of the transverse anisotropy; (ii) the manifestation of micro-buckling, leaving a lasting plastic imprint on the material; (iii) the emergence of localized field patterns, reminiscent of experimental findings on finger-like structures formation.