Intelligent Soft Actuators: Principles, Design, Applications and Challenges

ABSTRACT Intelligent soft actuators are built on stimulus‐responsive materials and structures capable of programmable mechanical transformations under external electrical, magnetic, optical, thermal, and pneumatic stimuli. Their compliance and adaptability enable artificial muscles, biomedical engineering, and drug delivery, which respectively face durability, biosafety, and release‐control bottlenecks. This review provides a comprehensive overview of the operating principles, material systems, and design architectures underlying major categories of intelligent soft actuators, including electroactive polymers and dielectric elastomers, ionic and hydrogel‐based actuators, magnetoactive elastomers, photothermal and photochromic materials, shape‐memory and thermally driven systems, as well as pneumatic and hydraulically amplified actuators. We systematically analyze their actuation performance, response dynamics, energy efficiency, material constraints, and integration compatibility. Recent advances in multimaterial three‐dimensional (3D) printing, micro‐ and nanostructuring, interfacial engineering, and scalable molding and assembly techniques are summarized with an emphasis on how fabrication strategies influence actuator durability, miniaturization, multifunctionality, and system‐level performance. Finally, we highlight cross‐cutting challenges, including limited long‐term stability, low energy efficiency in certain mechanisms, difficulties in closed‐loop control and sensing integration, and obstacles in achieving high‐force, high‐speed, and high‐strain actuation simultaneously. Emerging opportunities in hybrid actuation, bioinspired architectures, intelligent materials, and co‐designed sensing‐actuation systems are discussed to guide future research.