by Keyword: Softening

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Asadipour, N., Trepat, X., Muñoz, J. J., (2016). Porous-based rheological model for tissue fluidisation Journal of the Mechanics and Physics of Solids , 96, 535-549

It has been experimentally observed that cells exhibit a fluidisation process when subjected to a transient stretch, with an eventual recovery of the mechanical properties upon removal of the applied deformation. This fluidisation process is characterised by a decrease of the storage modulus and an increase of the phase angle. We propose a rheological model which is able to reproduce this combined mechanical response. The model is described in the context of continua and adapted to a cell-centred particle system that simulates cell–cell interactions. Mechanical equilibrium is coupled with two evolution laws: (i) one for the reference configuration, and (ii) another for the porosity or polymer density. The first law depends on the actual strain of the tissue, while the second assumes different remodelling rates during porosity increase and decrease. The theory is implemented on a particle based model and tested on a stretching experiment. The numerical results agree with the experimental measurements for different stretching magnitudes.

Keywords: Cell remodelling, Cell rheology, Fluidisation, Softening, Viscoelasticity

Muñoz, J. J., Conte, V., Asadipour, N., Miodownik, M., (2013). A truss element for modelling reversible softening in living tissues Mechanics Research Communications , 49, 44-49

We resort to non-linear viscoelasticity to develop a truss element able to model reversible softening in lung epithelial tissues undergoing transient stretch. Such a Maxwell truss element is built by resorting to a three-noded element whose mid-node is kinematically constrained to remain on the line connecting the end-nodes. The whole mechanical system undergoes an additive decomposition of the strains along the truss direction where the total contribution of the mid-node is accounted for by using a null-space projection and static condensation techniques. Assembling of such line-elements in 3D networks allows us to model extended regions of living tissues as well as their anisotropies.

Keywords: Maxwell, Null-space, Reversible softening, Truss, Viscoelasticity