Mechanical properties of sonication-initiated silk fibroin hydrogels. (A) Yield strength at 2% offset, (B) “traditional” elastic modulus calculated from the tangent at 5% strain of hydrogels prepared from silk fibroin aqueous solutions at various sonication treatments (30, 40, and 50% power output (Amp) for 30 seconds). (C) Equilibrium modulus of hydrogels prepared from 4%, 8% and 12% (w/v) silk fibroin aqueous solutions (at 50%, 50% and 30% amplitudes, respectively). Values are average ± standard derivation of a minimum of N=4 samples.