Thermally Responsive Architected Actuators with Programmable Shape Morphing and Tunable Stiffness

Abstract

Biological organisms excel in dynamically reshaping their bodies to navigate and manipulate ever-changing environments, and some can even tune their mechanical properties for enhanced adaptability. Many existing shape-morphing robots rely on the inherent softness of materials or structures, which sacrifices load-bearing capacity. Despite efforts to achieve both morphing and stiffness tuning in one system, these strategies often rely on separate mechanisms, such as heating liquid metal components to reduce rigidity before employing other mechanisms to change the shape, leading to bulky and complex systems that limit practicality and scalability. Here, a tunable-stiffness architected morphing structure (TSAMS) is introduced, which unifies shape morphing and tunable stiffness in a single, compact platform. By combining 3D-printed tessellated particles with shape memory alloy springs, TSAMS transitions smoothly from soft to rigid states, exhibiting a ≈308 times increase in bending stiffness while concurrently executing intricate shape transformations through electrothermal actuation. This design is demonstrated with the following robotic applications, including rolling robots that can explore diverse terrains by climbing slopes, avoiding obstacles, and carrying loads; compact manipulators that lift objects nearly 50 times heavier than themselves; and snake-inspired robots performing undulation and sidewinding gaits. These results highlight TSAMS's potential to advance next-generation soft robots and bioinspired systems that demand both dynamic shape reconfiguration and robust structural performance in diverse operating conditions.