Aloe Leaves-Inspired Multi-Stimuli Bidirectional Bending Self-Sensing Actuator for Smart Solar Panel.

Soft actuators with multi-stimuli response have shown promising applications in soft intelligent robots. However, most soft actuators are limited by the unidirectional actuation and self-perception capabilities. Here, a bilayer self-sensing actuator with bidirectional actuation is proposed, which showed exceptional bidirectional actuation, self-sensing of temperature and moisture, and smart solar panel. The actuator layer consisted of the powerful hygroscopic sensitivity of poly(vinyl alcohol) (PVA), poly(sodium styrene sulfonate) (PSS), and the conductive carbon black (CB). The structural layer is hydrophobic polyurea (PUU). The bilayer self-sensing actuator is bent to one side under NIR or temperature stimulation (curvature reaches 3.8 cm) and bent to opposite side with moisture stimulation (curvature reaches -4.6 cm). Moreover, various bionic robots, weightlifting, and selective grasping robots are demonstrated. Simultaneously, owing to CB gradient, the bilayer sensing actuators can detect movement in different bending directions with a fast response speed (82 ms). In addition, when moisture increased, the smart solar panel bent to downward and cleaned the debris. Upon the sunshine, the smart solar panel faced to sun and maximized power output. More interestingly, the smart solar panel can monitor its bending degree and orientation. The proposed bilayer self-sensing actuator paved the way for advancements in artificial intelligence robots.