Cell-substrate interaction model is illustrated on the right.

<p>The biological details of the mechanisms involved in cell spreading are reduced to four major model components, labeled (a)-(d) in the right panel titled “Reduced mathematical model”. Both the cell and the substrate are two dimensional. The rheology of the cell is determined by local concentrations of filaments, organelles, and additional macromolecules, and upon applying an external force via microindentation, the cytoplasmic forces undergo relaxation [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0171430#pone.0171430.ref026" target="_blank">26</a>]. We assume the average material properties of the cell to be hypoelastic (a), and we assume that the deformable substrate is linearly elastic (d). Actin-based cell movement [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0171430#pone.0171430.ref024" target="_blank">24</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0171430#pone.0171430.ref027" target="_blank">27</a>] is described by an active rate of deformation tensor (b). The interaction between cell and substrate occurs via the FAs, which are modeled as collections of discrete linear springs (c). A description of the dynamic FA complex is simplified and written as stress dependent evolution of a single scalar field representing the volume fraction of the entire FA complex [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0171430#pone.0171430.ref004" target="_blank">4</a>].