Deformation mechanism of the dual thermo-sensitive hydrogel bilayer structure

Abstract Thermo-sensitive hydrogel is a smart soft material that undergoes significant volume deformation in response to temperature changes, making it highly applicable in soft smart actuators. However, traditional thermo-sensitive hydrogel bilayer structures are often characterized by slow response rates and limited unidirectional bending capabilities. To overcome these limitations, a new thermo-sensitive hydrogel bilayer structure with faster response and bidirectional deformation is proposed in this work. This structure consists of two active thermo-sensitive hydrogel layers with different thermo-sensitive effect, in which one shrinks and the other swells when the temperature changes. The hydrogels with the fastest temperature response are identified by optimizing the monomer fraction and used to create the bilayer structure. The deformation states of the dual thermo-sensitive hydrogel bilayer structure are controlled by regulating the phase state of the both layers, resulting in different deformation patterns under varied temperature in experiments. We have established a model to describe the deformation of the bilayer structure. Finally, the capability of the bilayer structure to mimic human body movements and the blooming and wilting of flowers is demonstrated. This work reveals the deformation mechanism for a novel dual thermo-sensitive hydrogel bilayer structure, which holds great significance for the advancement of soft smart actuators.