Overcoming response-recovery kinetic mismatch in soft actuators via synergistic material design for multimodal moisture-responsive actuation

Abstract

Moisture-responsive soft actuators are widely used in robotics, medical devices, and wearable technologies, offering significant advantages by enabling movement and deformation without the need for complex power supplies or external devices. Traditional moisture actuators face a mismatch between response and recovery speeds, limiting their performance and stability in practical applications. In this study, a monolayer composite film (APCP) is developed, combining agarose (AG), polyvinyl alcohol (PVA), amino-functionalized multiwall carbon nanotubes (MWCNTs-NH₂), and phytanic acid (PA) to create a high-performance moisture-driven soft actuator. The APCP film, which is designed with a dynamic hydrogen bonding network, demonstrates a fast response (44.6° s⁻¹), efficient recovery (30.2° s⁻¹), and excellent mechanical properties (tensile strength of 71.9 MPa) under natural moisture conditions. The film enables various motions such as bending, rolling, and self-oscillation when exposed to moisture, and is successfully applied in soft gripper robots, autonomous seeding containers, and self-driven sailboats on water. Its innovation lies in solving the traditional response-recovery mismatch issue through material and structural optimization, while providing both environmental adaptability and energy-independent operation. This work provides new ideas for the application of moisture-responsive actuators in intelligent robotics, micro-actuators, wearable devices, and environmental monitoring.