Multifunctional gradient hydrogel with ultrafast thermo-responsive actuation and ultrahigh conductivity

Bioinspired hydrogels with both outstanding actuation and conductivity still remain challenging. Here, we use a simple and universal method to fabricate an octopus-tentacle inspired multifunctional gradient hydrogel with both ultrafast thermo-responsive actuation and ultrahigh conductivity. The gradient network structure, formed by rapid precipitation of nanosilver flakes producing hydrophilic differences between two sides within the hydrogel, endows the hydrogel with ultrafast actuation (52.3 degrees s(-1)). In addition, nanosilver flakes also provide the hydrogel with ultrahigh conductivity (>1231 S m(-1)) due to the formation of conductive pathways by rapid hydrogel volume shrinkage under thermal stimulation. Meanwhile, the hydrogel exhibits high sensitivity (gauge factor 14.66 within a wide strain range of 500%) and strong antibacterial properties. With these great properties, we firstly assemble the hydrogel as soft actuators (gripper and jack), where the gripper can firmly grasp and release the target object within only 8 s and 1 s, respectively. Secondly, we use the hydrogel as a wearable electronic device that enables precise detection of human motion and physiological signals. Finally, we realize smart circuit switches by combining great actuation and conductivity. Our multifunctional hydrogel offers promising opportunities for intelligent biomaterials, soft robotics and flexible sensors.