Copper‐Based Conductive Nanoinks: Scalable Synthesis via Continuous‐Flow Microwave‐Assisted Polyol Process

Metallic copper nanoparticles are a promising alternative to gold and silver in printed electronics due to their excellent electrical and thermal conductivity. However, their synthesis is often hindered by rapid oxidation and limited scalability. This work presents a microwave‐assisted polyol process for the rapid and scalable production of metallic Cu micro‐ and nanoparticles, performed in air without the need for an inert atmosphere. Ethylene glycol acts as both solvent and reducing agent, while lignin serves as a renewable capping agent. Reaction time is reduced to 10 min in batch mode, and the process is scaled up to a continuous‐flow microwave system, achieving production rates of ~5 g h −1 . Particle sizes range from 800 to 40 nm depending on lignin content and metal seeding. After pressure or low‐temperature (150 °C) treatment, the materials reach conductivities between 30 and 100 μΩ·cm. These metallic copper nanoparticles show strong potential for use in sustainable conductive inks for flexible and printed electronics.