Multi-Responsive 4D-Printed Soft Active Material toward Shape-Reconfigurable Actuators

The development of 4D-printed soft active material (SAM) with programmable shape transformations and multifunctional properties remains a critical challenge for soft active materials. In this study, a 4D-printed, dual-responsive SAM is designed by integrating a 4-arm star poly(N, N-dimethyl acrylamide)-block-poly(dimethyl amino ethyl methacrylate)-Br (4-arm star (PDMA-b-PDMAEMA)₄-Br) diblock copolymer with acrylic acid (AA), enabling precise shape morphing, tunable mechanical performance, and multi-stimuli responsiveness. The SAM demonstrated excellent 3D printing, enabling the fabrication of complex 3D architectures with pre-designed infill patterns. It exhibited high shape fixation and rapid shape recovery upon thermal activation at 44 °C. Moreover, its pH-responsive swelling behavior facilitated selective dye removal, achieving ≈96% uptake of a model cationic dye at pH 10.5 and ≈65% uptake of a model anionic dye at pH 4.5. The SAM-based robotic actuator successfully lifted weights, showcasing its potential for soft robotics applications. The integration of shape-memory behavior with functional applications highlights the potential of this smart material in sustainable environmental technologies and advanced safety systems. These findings highlight the versatility of SAM for 4D-printed adaptive systems, offering promising applications in biomedical engineering, and intelligent actuators.