A Review on Printing of Responsive Smart and 4D Structures Using 2D Materials

Abstract 3D printing is revolutionizing the manufacturing sector due to the myriad of materials and techniques available. Furthermore, it allows decentralized production sites for both industry and the public. However, it is restricted to static structures that cannot react to external stimuli or adapt to the environment and are, therefore, not suitable for functional and motile parts. Recently, two approaches are proposed to give dynamism to 3D printed structures: the printing of “stimulus‐responsive” (a.k.a. smart) materials and “4D printing,” the first implying features change due to a stimulus while the second indicating the time evolution of properties after a stimulus activation. Nanomaterials, particularly 2D nanomaterials, exhibit a broad and distinctive combination of features. Thus, they are highly effective at enabling this dynamism due to their morphological, optoelectrical, and mechanical properties. This review summarizes recent advances in 3D/4D printing of smart deformable and stimuli‐responsive materials which utilize 2D nanomaterials. The benefits of 2D materials in this framework are summarized, and how to translate their potential into 3D/4D printing is also discussed. The most promising achievements to date are deformable piezoresistive materials for strain sensing, Joule heaters, and actuators. Future advancements and possible upcoming application areas are finally proposed.