Active over-relaxation and stress memory of living tissues after osmotic shock

Abstract Recent experiments show that a soft biological tissue generated by self-aggregation of different cell lines around two elastic pillars produces a traction that can be measured in terms of deflection of the beams themselves. When dextran is added to the fluid surrounding the tissue, an osmotic pressure is applied to the sample which exhibits fast compression. On a longer time scale, of approximately 30 min, the material elongates along the pillar inter-axis (the direction of active stress) up to a length that is even larger than the pre-shock one. We address an active mechanical explanation of such an unexpected behaviour by investigating the peculiar poroelastic nature of the tissue material, made up of an active solid component that can remodel its dynamic activity on the basis of external loads.