Introduction to mask-free patterning of metal lines using aerodynamically focused nanoparticle system

We introduce an aerodynamically focused nanoparticle (AFN) system that precisely controls the flow of nanoparticles (NPs) to fabricate line patterns by aerodynamically controlling NP flow upon varying the discharge pressure without using any solvent or binders, which accompanies post processes. We optimized the air compressor pressure and performed a two-step excitation process to ensure high-quality deposition so that the AFN system usefully fabricates line patterns much narrower than its nozzle diameter. The narrower line patterns showed lower resistivities than those for wider patterns. It was observed that when NPs were concentrated at a point, their line widths decreased, while the NP deposition was dense. XRD and TEM analysis revealed that the NPs were highly focused and accelerated as crystal defects were developed. The NPs were densely deposited and adhered well to the substrate. Finally, a bending test revealed that the printed 35-μm-wide lines had the smallest resistance change during 300 cycles. Therefore, an innovative printing system called the AFN system has proven its potential to replace semiconductor patterning and inkjet printing for the application of flexible electronics. Impact statement Globally, the need for eco-friendly process development is becoming increasingly important. To follow this trend, we introduce the aerodynamically focused nanoparticle (AFN) system that precisely controls flow of nanoparticles (NPs) to fabricate line patterns by aerodynamically controlling NP flow without using any mask, which subsequently follows etching with toxic chemicals, and solvent or binders, which accompanies post processes. Therefore, this innovative system can obtain the desired pattern in a simple and eco-friendly manner. We optimized the air compressor pressure and performed a two-step excitation process to ensure high-quality deposition so that the AFN system usefully fabricates line patterns much narrower than its nozzle diameter. In this research, the flow of NPs can result in a narrow line pattern, which is 1/24 of the size of the nozzle. The narrower line patterns showed lower resistivities than those for wider patterns. When NPs were concentrated at a point, their line widths decreased, while the NP deposition became dense. XRD and TEM analysis revealed that the NPs were highly focused and accelerated as crystal defects were developed. Therefore, an innovative printing system called the AFN system, has proven its potential to replace