A novel SS/Cu composite with bioinspired helical-lamellar-interpenetrated structure by direct ink writing and pressureless infiltration

Inspired by the outstanding performance of natural materials due to their distinctive structures, we utilized direct ink writing (DIW) and pressureless infiltration techniques to design and manufacture innovative SS/Cu composites featuring helical lamellar interpenetrated structures (HLIs). DIW was used to construct SS porous scaffolds with hierarchical pores showcasing HLIs. By taking advantage of the favorable wettability between SS and Cu, we successfully achieved spontaneous Cu infiltration into the SS scaffolds through capillary force, thereby creating SS/Cu composites. Throughout the infiltration process, Cu first occupied smaller pores within the SS filaments before filling up larger channels between them; this resulted in residual pores within Cu matrix. The effects of structural parameters on both scaffolds and composites compressive strength was evaluated. Our findings demonstrate that increasing the helical angle of HLIs gradually enhanced the compressive strength of the SS scaffolds while introducing significant anisotropy. In contrast, due to a high volume fraction (∼60%) of Cu filler, SS/Cu composites exhibited nearly isotropic compressive strength and electrical conductivity. This work presents a demonstration case aiming to develop a scalable 3D printing method for fabricating composites and advancing heterogeneous structural design principles in metallic materials.