Fig. 5. Programming of protein hydrogels with cations and morphing via chemomechanical changes.

(A) BSA hydrogels were casted in cylindrical shape in PTFE tubes (top left) and programmed in a spring shape using a negative cast, by immersion in 2 M Zn²⁺ solution (top right) or 1.5 M Cu²⁺ solution (middle right) for 30 min; BSA hydrogels were produced in a flower shape using a silicone mold (bottom left) and programmed into a ring, by immersion in 2 M Zn²⁺ solution for 30 min (bottom right). (B) Morphing from the programmed shape into the casted shape of BSA hydrogel upon immersion in regular Tris buffer at time 0 (left) and 5 min (right) for the hydrogels from (A). Movies S1 and S2 accompany this figure. (Photo credit: Luai R. Khoury, UWM; Marina Slawinski, UWM).