Rewritable wavelength-selective hydrogel actuators grafted with fluorophores.

Recent efforts have focused on developing stimuli-responsive soft actuators that mimic the adaptive, complex, and reversible movements found in natural species. However, most hydrogel actuators are limited by their inability to combine wavelength-selectivity with reprogrammable shape changes, thereby reducing their degree of freedom in motion. To address this challenge, we present a novel strategy that integrates these capabilities by grafting fluorophores onto temperature-responsive hydrogels. By harnessing the photothermal effects of fluorophores responsive to specific light wavelengths, we achieve wavelength-selective shape morphing under light irradiation at wavelengths of 405, 520, and 638 nm. Furthermore, iterative chemical bleaching of the fluorophores allows for multiple rewritable shape configurations from a single actuator. Using this approach, we successfully demonstrate multiple shape configurations with a single hydrogel actuator that are precisely controlled with both wavelength-selectivity and rewritability. This approach significantly advances the field of soft robotics, paving the way for adaptive, reprogrammable actuators that could serve as intelligent, light-driven soft robots in the future.