Fabrication of Nano\nCopper Highly Conductive and Flexible\nPrinted Electronics by Direct Ink Writing

Nanoscale metals have emerged as crucial materials for\nconductive\ninks in printed electronics due to their unique physical and chemical\nproperties. However, the synthesis of high-precision and highly conductive\ncopper ink remains a challenge. Herein, a high-precision, highly conductive,\nand oxidation-resistant nanocopper ink was synthesized to fabricate\nhighly conductive and flexible printed electronic devices. Copper\nnanoparticles with a particle size of only 8.5 nm, a controllable\nstructure, and excellent oxidation resistance were synthesized by\nthe alcohol phase reduction method. The conductive ink was formulated\nwith ethylene glycol, ethanol, and isopropanolamine (IPA) as the solvent,\nexhibiting excellent printability and sintering reducibility. Fluid\ndynamics simulations were employed to investigate the influence of\nprinting parameters on the circuit forming performance, enabling precise\ncontrol over the printing process. The sintering behavior of copper\nnanoparticles with varying particle sizes was investigated by combining\nexperiments with molecular dynamics (MD) simulations. Highly conductive\nand flexible circuits were fabricated using direct ink writing (DIW)\nunder low-temperature sintering, exhibiting a low resistance level\nas low as 1.9 μΩ·cm. Moreover, the circuit demonstrated\nan excellent adhesion performance and bending flexibility. The developed\ncopper ink demonstrates outstanding printing potential for applications\nin flexible electronics, advancing the field of flexible printing\nand wearable electronic devices.