Fig. 2.

Free-floating (a), uniaxially constrained (b), and biaxially constrained (c) fibroblast-seeded collagen gels (i.e., tissue equivalents) are observed to contract substantially over the first hours to days. Cells residing in the gel initially spread and attach to surrounding collagen fibers. Cellular contraction then compacts the surrounding matrix thus stressing the fibers. d Biaxial testing device reported in Eichinger et al. (2020). Sensors are installed along two axes to record the development of tension in a cruciform gel