Intelligent materials in 3D printing: A journey from additive manufacturing to 4D printing

Additive Manufacturing (AM), commonly known as 3D printing, over three decades, emphasizing its transformative ability to create intricate structures in a single unit. The growing popularity of AM is attributed to continuous technological advancements and its application across diverse materials, responding to the demand for personalized products, shorter development cycles, sustainability, and new business models. Despite AM's strengths, the limitations of materials used in the process prompt the integration of intelligent materials, particularly in the emerging field of 4D printing. The focus shifts to intelligent materials, also known as smart materials, which respond to external stimuli, offering controlled transformations or shape changes post-fabrication. The narrative explores programmable matter, or 4D printing, where materials exhibit time-induced dynamics, introducing a fourth dimension to AM. Intelligent materials such as piezoelectric, shapememory, giant magnetostrictive, and nanomaterials extend the scope of applications from sensors to artificial muscles. The review discusses diverse 3D printing technologies in conjunction with intelligent materials, envisioning a future where these materials redefine additive manufacturing landscapes. AM technologies showcase their compatibility with intelligent materials and their potential to revolutionize various industries. The compatibility of intelligent materials with these technologies opens avenues for creating complex, functional, and customized objects with improved mechanical, thermal, and electrical qualities. 4D printing and the fusion of intelligent materials with bioinspired design principles offer a glimpse into the future of adaptive and functionally superior 3D-printed objects.