Figure 6.

A biomimetic valve based on bistrip hydrogel. (a) After simultaneous polymerization of the pH-sensitive strips. The hydrogel composition is the same as that described in Fig. 4e. (b) After polymerization of the non-pH-sensitive strips to form the bistrip hydrogel valve with anchor. The prepolymer mixture for the non-pH-sensitive hydrogel consists of HEMA, EGDMA (1.0 wt %), and Irgacure 651 (3.0 wt %). (c) When exposed to basic solution, the bistrip hydrogel expands and curves to form a normally closed valve. The bistrip valve can be pushed open (d) to allow flow in one direction (from left to right) while restricting flow in the opposite direction (e). (f) When exposed to acidic solutions, the valve is deactivated, returning to the permanently open state. (Bars = 500 μm.)