Fabrication of Nano Copper Highly Conductive and Flexible Printed Electronics by Direct Ink Writing.

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