Mechanistic Study on Regulating the Aspect Ratio of Silver Lines in Dry Aerosol Jet Printing via Focusing Ratio

This study systematically investigated the regulatory mechanism of the focusing ratio σ (σ = sheath gas flow rate Q_s/ carrier gas flow rate Q_c) on the morphology of conductive silver lines, aiming to achieve high resolution and high aspect ratio in dry aerosol jet printing (DAJP). Combining flow field simulations with experimental process analysis revealed that increasing σ significantly enhanced the aerodynamic focusing effect, narrowing the particle stream trajectory and consequently improving line resolution. At the same σ, deposited line width remained largely consistent under different Q_c, indicating that σ was a dimensionless parameter controlling line width independently of Q_c. Experimental results showed that the line width (W) correlated negatively with both σ and the stage velocity (V_s), but positively with Q_c; the line height (H) correlated positively with σ and Q_c, and negatively with V_s. Under a fixed σ, increasing Q_c while decreasing V_s effectively enhanced H, achieving high resolution and high aspect ratio (AR). Based on the maximum flow threshold and the critical stage velocity, an optimized process window for Q_c = 200 sccm was established, successfully fabricating high-quality silver lines with W = 103.34 μm, H = 7.82 μm, and AR = 7.56%. Subsequently, post-treatment by muffle furnace sintering (200°C, 60 min) reduced the resistivity to 23.51 μΩ·cm, meeting the conductivity requirements for flexible electronic devices. This study provided a theoretical foundation for parameter design and process control of high-precision three-dimensional metallic structures using DAJP.