“…[265,[266][267][268][269][270][271] The common materials that can be 3D-printed include metals/ alloys, [272][273][274][275] (e.g., aluminum (Al) alloys, stainless, titanium, and its alloys), polymers and composites, [276][277][278][279] (e.g., polycarbonate (PC) and polylactic acid (PLA)), ceramics and biomaterials, (e.g., cellulose, silk, chitosan) etc. [61,174,249,[280][281][282][283] However, the fatigue strength of 3D printed objects is usually unsatisfactory due to the porosity and surface roughness of the printed structures, which necessitates the complex and expensive postmanufacturing treatments, e.g., hot isostatic pressing (HIP) and heat treatments, for improving the mechanical strength of 3D printed objects. [249,255,284,285] Moreover, the soft mechanical nature of polymers and biomaterials limits their printability in 3D structures.…”