Visual multi-triggered sensor based on inverse opal hydrogel

Smart hydrogels are regarded as novel sensors due to large reversible volume change in response to external stimuli. Here we prepared a novel visual multi-triggered sensor based on inverse opal hydrogel (IOH) that responses to pH, temperature and light, respectively. The hydrogel was composed of hydrophilic pH and temperature responsive poly(dimethylaminoethyl methacrylate) (PDMAEMA), and light responsive spiropyran-containing segment. When the pH decreased, the sensor changed its structural color from blue to orange-red, and the structural color was reversibly recovered by increasing pH. In addition, the color of sensor can be controlled to change from green to violet while applying a temperature field. Furthermore, the reflection peak of IOH exhibited obvious shifted behavior by UV/visible irradiation. Repeated condition changes revealed that the sensor has a long lifetime.