Figure 4.

Hydrogel degradation. a) Series of images showing the return of the thiol–acrylate gel to the liquid state, in which [urea]=0.09 m, [urease]=0.85 mg mL⁻¹ (29 units mL⁻¹), [ETTMP]₀=0.06 m, and [PEGDA]₀=0.08 m. b) Dynamic rheology with storage modulus G′ as a function of time. c,d) Time to return to the liquid state as a function of the urea (c) and ETTMP concentrations (d). Concentrations of other components: [ETTMP]₀=0.1 m, [urea]₀=0.03 m, [urease]=0.5 mg mL⁻¹ (17 units mL⁻¹); the ETTMP/PEGDA molar ratio was 2:3; T=23 °C.