Highly programmable 4D printed multi-shape gradient metamaterials and multifunctional devices

Abstract Metamaterials, owing to their exceptional physical characteristics that are absent in natural materials, have emerged as a crucial constituent of intelligent devices and systems. However, there are still significant challenges that necessitate immediate attention, as they have considerably constrained the applicability of metamaterials, including fixed mechanical properties post-fabrication and restricted design freedom. Here, thermo-responsive, photo-responsive, electro-responsive, and magneto-responsive shape memory polymer nano-composites were developed, and shape memory gradient metamaterials were fabricated using multi-material 4D printing technology. The correlation mechanism between the design parameters and the mechanical properties of multi-responsive gradient metamaterials was systematically analyzed, and the highly designable and programmable configuration and mechanical properties of the gradient metamaterials were realized. More importantly, 4D printed multi-responsive shape memory polymer gradient metamaterials can be programmed in situ without additional infrastructure for multi-functional mechanical functions, paving the way for the realization of multiple functions of a single structure. Based on the multi-responsive gradient metamaterials, 4D printed digital pixel metamaterial intelligent information carriers were fabricated, featuring customizable encryption and decryption protocols, exceptional scalability, and reusability. Additionally, 4D printed gradient metamaterial logic gate electronic devices were developed, which were anticipated to contribute to the development of smart, adaptable robotic systems that combine sensing, actuation, and decision-making capabilities.