Figure 6.

Axial stress exerted by the tissues at different levels of uniaxial compression, from 0 up to 40% with 10% increments. The amount of stress for healthy (blue) and cancer (red) tissues was calculated by dividing the normal force (F_N) registered by the force transducer by the sample surface area in contact with the rheometer plate. (A) Stress–relaxation for cancer and healthy tissues; (B) stress–relaxation normalized to the initial stress just before each compression step; (C) stress–relaxation course for cancer tissue in 20% compression with a two-component stress–relaxation model: σ(t) = 1 – σ_∞(1 + e^–t/τ), where σ(t) is the reduced relaxation function and σ^∞ and τ are the fitting constants for the equilibrium modulus and relaxation time constant, respectively; (D) exponential decay time (t) for cancer and healthy tissues at different levels of compression.⁵⁶