One class of state-of-the-art lightweight, energy-efficient materials with enhanced material properties is "architected cellular solids." Their exotic properties (e.g., high strength-to-weight ratio, high energy absorption capability and tunable multiphysical properties) mainly stem from their rationally designed underlying architectures (e.g., cell topology and cell connectivity) and partially from the properties of their constituent materials. [1] Cellular solids, so-called cellular-based "metamaterials," upon showing unprecedented properties, have recently received considerable attention due to their potential applications in aerospace, automotive, energy, robotics and biomedical sectors as high-performance lightweight panels, energy absorbers, morphing structures, noise reduction, waveguide devices, programmable battery electrodes, and bioimplantable medical devices. [2] Recently, advances in "3D printing," interchangeably called "additive manufacturing" (AM), have shed light on strategies for design and realization of advanced materials (including "cellular solids" and "architected metamaterials") with controlled material composition and architectural complexity. A large number of studies have been conducted to investigate the correlation between specific mechanical properties and the architecture of 3D-printed advanced materials. [3] Fast prototyping, material saving, waste minimization, design freedom, and the capability to manufacture complex architectures are the main 3D printing advantages. [4] 3D printing is a fabrication process for constructing free-form materials and structures from a computer-aided design model. The printing process typically involves layerupon-layer fabrication that enables the production of complex geometries that would be impossible by conventional manufacturing processes. [5] Several methods can be adopted for 3D printing: direct metal laser sintering (DMLS), selective laser melting (SLM), and electron beam melting (EBM) for printing metallic powders; selective laser sintering (SLS) for printing polymeric and metallic powders; laminated object manufacturing (LOM), direct foam writing, 3D extrusion freeforming of ceramics (EFF), and lithography-based ceramic manufacturing (LCM) for ceramic-based materials; stereolithography apparatus (SLA) and digital light projection (DLP) for printing photopolymeric resins; and fused deposition modeling (FDM) for printing thermoplastic polymers. [6] The simplicity, reliability, affordability (minimal waste, low processing and operational cost), multimaterial (multinozzle) printing capability, and adaptability to new materials, and composites have made FDM one of the most
