3D Printing of Auxetic Metamaterials with High‐Temperature and Programmable Mechanical Properties

Abstract Negative Poisson's ratio mechanical metamaterials with typical auxetic behavior have great potential applications in aerospace and flexible electronics. However, the structure and properties of conventional mechanical metamaterials are fixed after fabrication, which greatly limit their applications. In recent years, some progress has been made in combining shape‐memory polymers (SMP) with 4D printing to develop auxetic metamaterials with programmable mechanical properties. Unfortunately the low‐temperature phase change of conventional SMP greatly hinders the further development of 4D printed mechanical metamaterials in the field of high‐temperature and high‐strength service. Here, the high‐performance polymer polyetheretherketone (PEEK) as the printing material is selected and a new mechanical metamaterial is prepared using fused deposition molding technology to program the material structure and properties by designing the structural parameters of the metamaterial mesh structure. In addition, thermal analysis shows that the printed samples have good thermal stability, including a phase change temperature of 170 ° C, an initial thermal decomposition temperature greater than 500 ° C, and qualified shape memory properties. Combining structural design with the shape memory properties of PEEK, reconfigurable metamaterial structure and properties are realized. Finally, 2D digital mesh structure is designed and fabricated with selective stretching strain positions and a stretchable circuit with constant resistance.