Fig. 2.

Calculating local tissue stresses from observable MSG deformations. a Shear rheometry on bulk, fluorescently-labeled polyacrylamide hydrogels indicates linear elastic deformations over large strains, with negligible loss modulus. b Deformation of fluorescently labeled polyacrylamide hydrogel strings were used to determine that the Poisson’s ratio of the material was constant (ν = 0.3) over the working range of expected deformations (scale bar = 5 mm; n = 7). c To characterize the mechanical properties of individual MSGs, their deformations were observed under an applied osmotic pressure of 67 Pa. The apparent shear modulus of the material was found to be G = 60 Pa ± 3.5 Pa, and was independent of the MSG sizes used in these experiments (scale bar = 50 μm; n = 24). d–e Axial (ε_z) and radial (ε_r) strains in an MSG are swept parametrically to determine the d axial (σ_z) or e radial (σ_r) stresses associated with each combination of strain. Using these simulations, observations of MSG deformation in the radial and axial directions can be used to determine the unique combination of stresses present at that location