# Fabrication of Copper Nanowires Highly Conductive and Flexible Circuits by Direct Ink Writing

## TL;DR

This paper presents a method to create highly conductive and flexible copper nanowire circuits using direct ink writing, enabling low-cost, high-precision flexible electronics.

## Contribution

A novel liquid-phase reduction method to synthesize high-aspect-ratio copper nanowires with excellent oxidation resistance for DIW printing.

## Key findings

- Copper nanowires with an aspect ratio of up to 2884 were synthesized using a liquid-phase reduction method.
- Flexible circuits with a resistivity of 2.11 μΩ·cm were fabricated using DIW and thermal sintering.
- The circuits showed excellent adhesion, flexural behavior, and water resistance.

## Abstract

Direct ink writing (DIW) has emerged as a promising method for fabricating flexible electronics. Copper nanowires are a key material for the conductive inks required for this technology. However, copper nanowires suffer from significant challenges, including low aspect ratios, poor oxidation resistance, and difficulty in printing. In this study, a liquid-phase reduction method was used to synthesize copper nanowires with a high aspect ratio (up to 2884) and excellent oxidation resistance. The conductive ink was prepared using ethylene glycol, isopropanolamine (MIPA), and ethanol as solvents. Rheological dynamics simulations were used to investigate the influence of printing parameters on ink printing accuracy, ultimately achieving precise control of the printing process. High-precision copper nanowire flexible circuits with a low resistivity of 2.11 μΩ·cm were fabricated under thermal sintering conditions using the DIW method. These circuits exhibited excellent adhesion, flexural behavior, and water resistance, demonstrating significant practical significance for the low-cost fabrication of high-precision flexible electronic devices.