pH and Thermo Dual-Responsive Fluorescent Hydrogel Actuator.

As one of the most important smart materials, fluorescent hydrogel actuators can produce both color and shape changes under external stimuli. In the present work, an effective approach to develop a novel fluorescent hydrogel actuator with pH and thermo dual responsiveness is proposed. Through incorporating pH-responsive perylene tetracarboxylic acid (PTCA), which is a typical fluorescent moiety with aggregation-caused quenching (ACQ) effect, into an anisotropic poly(N-isopropylacrylamide)-polyacrylamide (PNIPAm-PAAm) structure, the obtained hydrogel exhibits stable thermoresponsive shape deformation and switchable fluorescence performance upon a pH trigger. Therefore, fluorescence-quenching-based and actuation-based information can be revealed when exposed to UV light and immersed into warm water, respectively. Moreover, the thermoresponsive actuating behavior can be applied to further hide the fluorescence-quenching-based images. The present work may provide new insights into the design and preparation of novel stimuli-responsive hydrogel actuators.