Stimuli-responsive shape-morphing soft actuators: metrics, materials, mechanism, design and applications

The rapid development of flexible wearable devices and the integration of artificial intelligence (AI) in robotics have driven the evolution of soft actuators, positioning soft shape-morphing actuators at the forefront of cutting-edge research in soft robotics, intelligent devices, and bio-inspired engineering. Stimuli-responsive soft actuators are intelligent devices constructed from flexible materials capable of precise and controllable deformation in response to external stimuli, attracting growing scientific and technological interest. This review systematically delineates and evaluates critical performance metrics essential for evaluating actuator functionality. It offers a comprehensive analysis of the predominant stimuli-responsive actuating materials, elucidating their actuation mechanisms while critically examining their inherent advantages, limitations, and emerging research trajectories. Fundamental design principles are meticulously articulated to guide the development of next-generation shape-morphing actuators. Furthermore, this review extensively surveys diverse practical applications, underscoring the versatility and broad technological impact of stimuli-responsive soft actuators across multiple domains. Finally, key challenges in the current state-of-the-art and prospective research pathways are thoroughly discussed, aiming to foster the development and widespread adoption of soft actuators in both academic research and industrial applications.