“…in response to external stimuli, showing great promise in developing smart materials. Based on the interesting structure and excellent performance, such as remarkable flexibility, softness, superior absorption capacity in their swollen state, nontoxicity, biocompatibility, biodegradability and tunable mechanical properties [1,11] , polymer hydrogels have been used as superabsorbent materials [12] , for industrial wastewater treatment [13] , to build various of intelligent apparatus and actuators [14][15][16][17] , to control drugs delivery and release [18,19] , to engineer artificial muscles and tissue [20][21][22][23] . Hydrogels characterized by recognizing and responding specifc analytes such as human metabolites [24] , heavy metal ions [3,25,26] , anionic species [4,27] , etc.…”