Light- and humidity-driven fluorescence changeable soft robot enabled by water-gated photoinduced electron transfer pathway

Abstract

Intelligent soft biomimetic materials have been one of the focuses of scientific research in recent years. However, designing and fabricating biomimetic devices with multiple functions and responses remains a considerable challenge. In this study, a light and humidity dual responsive soft actuator was prepared by incorporating light-sensitive liquid crystalline networks (LCNs) and hydrophilic poly(2-carboxyethyl acrylate-co-acrylic acid) (poly(2-CEA-co-AA)) layers. Upon ultraviolet light exposure, shape morphing of the azobenzene-crosslinked LCN matrix deformed the composite film. Moreover, changes in relative humidity (RH) caused the bilayer film to undergo another mode of shape transformation due to swelling and deswelling of the hydrophilic poly(2-CEA) layer. Further, the fluorescence intensity of the film increased concurrently due to the presence of doped water-sensitive fluorescence molecules. Herein, this novel bimorph actuator demonstrated potential in the fabrication of intelligent soft robots because of the integration of dual responsiveness and synergistic behaviors. Hence, a light-directed smart walker was created through systematic design. The walker could detect water and adjust its motion and fluorescence intensity, demonstrating the practical application potential in the development of multifunctional soft robots capable of recognizing, responding, and self-adjusting. [Figure not available: see fulltext.].