Three-dimensional metamaterials based on discrete assembly to customize thermal expansion response under temperature stimuli

Three-dimensional (3D) metamaterials with the customizable thermal response under the temperature stimuli are of great necessity for engineering applications. However, current researches usually focused on the design strategy of these metamaterials and lack the integrated strategy throughout design and fabrication. Here, an integrating design-manufacturing-response workflow is established to develop a series of 3D metamaterials. Specifically, a construction strategy, which is based on discrete assembly, mortise-and-tenon structures and transition cube blocks, is proposed to connect the dissimilar and out-of-plane struts. Then, totally three classes of 3D complicated metamaterials made of Aluminum and Invar alloys are fabricated to export multi-directional customizable coefficient of thermal expansion (CTE). Additionally, the theory prediction, simulations and experiments are conducted to characterize the thermal responses. The results suggest that through reasonably modulating the geometrical parameters, all the fabricated metamaterials are capable of reaching the CTEs across from large positive, near-zero and negative values. Besides, the metamaterials PC and UN present the unidirectional customizable CTEs (-12.72 x 10(-6) similar to +42.73 x 10(-6)/degrees C and -12.54 x 10(-6) similar to +41.51 x 10(-6)/degrees C, respectively), while the metamaterials FS show the transversal isotropic CTEs (-10.89 x 10(-6) similar to +34.66 x 10(-6)/degrees C) and IS have the isotropic customizable CTEs (-10.18 x 10(-6) similar to +34.58 x 10(-6)/degrees C). Overall, these originally developed metamaterials open a new avenue for customizing the targeted thermal responses for engineering applications, where the thermal expansion is of high significance.