Temperature-Responsive Anisotropic Bilayer Hydrogel Actuators with Adaptive Shape Transformation for Enhanced Actuation and Smart Sensor Applications

Anisotropic bilayer hydrogel actuators are high-performance materials engineered to exhibit unique and programmable mechanical properties, including varying stiffness and directional bending capabilities, by integrating two hydrogel layers with distinct responses to stimuli. However, programming and constructing these bilayer hydrogels remains challenging due to their lack of mechanical robustness, rapid responsiveness, and dual-actuation capabilities, which hinder their practical applications and further development. Hence, developing a double-actuating bilayer hydrogel with a temperature-responsive and auxiliary layer could address these challenges. Herein, an anisotropic hydrogel actuator is developed using a simple and economical casting method, in which a unique multiasymmetric bilayer structure locked by an interfacial is fabricated. The as-prepared hydrogels demonstrate exceptional temperature-responsive bending abilities, achieving a 360 °C angle in just 8 s, and exhibit adaptive, complex shape transformation capabilities tailored to specific needs (e.g., two dimensional (2D) letters, leaves, flower, and butterfly hydrogel). Furthermore, the hydrogels possess excellent shape memory, mechanical strength, and conductivity. Additionally, gripper and humidity alarm prototypes made from the hydrogel are also successfully developed, illustrating that this approach opens new avenues for designing and producing smart hydrogels with practical applications in sensors, smart humidity alarms, and on-demand smart grippers and actuators.