Thermomechanical molding of three-dimensional nanoporous metamaterials with great crystallinity

Nanoporous metamaterials have garnered significant attention due to their unique combination of lightweight, high specific-surface-area, and small size effects. However, their mechanical performance is usually limited by structural imperfections introduced during conventional fabrication processes. In this study, we present a universal and cost-effective thermomechanical molding technique for directly fabricating three-dimensional (3D) crystalline metamaterials. Micropillar compression tests show that the nanoporous structures fabricated through this technique exhibit significantly enhanced mechanical properties, even with a yield strength 2 times higher than that of the corresponding bulk materials. Transmission electron microscope (TEM) characterization revealed the single-crystalline nature of the whole nanoporous structure, which can fully utilize the size effect of strength, that is, “the smaller the stronger”, thereby offsetting the reduction of effective load-bearing materials caused by porosity. Moreover, we demonstrate that the thermomechanical molding technique is highly versatile, enabling the fabrication of 3D nanoporous structures in a wide range of elemental metals, thermoelectric, semiconductor, and phase-change materials, offering a promising way for the development of next-generation functional nanoporous metamaterials.