Unveiling the Role of Coffee-Ring Effect in High-Resolution Rivulet-Type Conductive Line Formation

This study aims to investigate the effects of particle size and concentration on the formation of rivulet-type conductive lines based on detailed physical insights into the formation of coffee-ring patterns. Rather than being a phenomenon to be avoided, the coffee-ring effect can be strategically used to fabricate high-resolution conductive lines with multiring patterns. We first characterized the coffee-ring patterns formed by the evaporation of a single nanofluid droplet with silver particles. It was observed that increasing the particle concentration resulted in thicker and wider deposition patterns, with only minor dimensional variations caused by differences in particle size. Based on these insights, multiple nanofluid droplets were sequentially deposited, and their interactions were analyzed to form rivulet-type conductive lines, consequently determining the optimal center-to-center droplet spacing. Sheet resistance was measured using the well-known four-point probe method to assess the electrical performance. The results demonstrated that a higher particle concentration enhanced particle packing density, improved current flow, and significantly reduced sheet resistance.