Figure 5.

Tunable elasticity of cross-linked networks. (A) Given here are snapshots of a strained network (k_a = 1000 pN/μm, k_xl = 20 pN/μm) at γ = 0.1, γ = 0.25, and γ = 0.5. Color indicates stretching energy on each link, with green (darkest) being the lowest and yellow (lightest) being the highest. For all snapshots, t = γ × 1 s. (B) Given here is the potential energy of the network as a function of time shown at different strains γ₀ = 0.1 (circles), γ₀ = 0.25 (squares), and γ₀ = 0.4 (triangles), where t₀ = γ₀ × 1 s. The black dashed line shows the strain protocol. (C) Shown here is the strain energy density (w = U/XY) for various values of cross-linker stiffness k_xl. The blue dashed line indicates expected behavior for a linearly elastic solid (w ∝ γ²) and the green dashed line indicates strain stiffening behavior of w ∝ γ^3.5 as expected for semiflexible polymer networks (44, 47). (D) Given here is the power-law exponent of w(γ) as a function of cross-linker stiffness, evaluated by least squares fitting ln(w) as a function of ln(γ). To see this figure in color, go online.