Process and nozzle design for high-resolution dry aerosol direct writing (dADW) of sub-100 nm nanoparticles

One of the essential requirements to create nanoparticle (NP)-based applications and functions is the ability to control their deposition in specific locations. Many methods have been proposed, with wet direct writing (DW) techniques such as inkjet printing being the most employed. These methods generally depend on off-line and solvent-based NP synthesis leading to contamination and impurity in the final NP film as well as inhomogeneity in the deposition caused by solution-substrate interactions. This paper introduces a dry aerosol direct writing (dADW) method, which combines spark ablation-based and solvent-free NP synthesis with spatially selective deposition using aerodynamic focusing in a vacuum chamber. The challenge is to print high-resolution lines and spots of nanoparticles with a diameter < 100 nm. We study two aerodynamic nozzle concepts, a converging nozzle (CN) and a sheath gas nozzle (SGN), and investigate numerically how their design, as well as operating parameters, relate to the deposition process performance. This is quantified by three criteria: contraction factor, focusing ratio, and collection efficiency. We also compared our numerical results to experimental assays by manufacturing two SGNs and three CNs and evaluating the performance of each nozzle in terms of resolution, sharpness and thickness of the line. Using one of the SGN designs with an outlet diameter of 248 mu m and an aerosol to total flow rate ratio of 0.17, we achieved a high-resolution line with a width of 67 mu m, i.e., equal to 27% of the nozzle diameter, when printing < 100 nm Au NPs. The presented additive manufacturing method enables, therefore, the creation of high-resolution and sharp patterns of metallic nanoparticles, which can be employed in a wide range of applications, ranging from interconnects to optical and gas sensors.

Automated summary

This paper introduces a dry aerosol direct writing (dADW) method for the spatially selective deposition of nanoparticles. Two aerodynamic nozzle concepts were studied and their design and operating parameters were numerically investigated for their performance in the deposition process. Experimental and numerical results demonstrated the ability of the method to print high-resolution patterns of metallic nanoparticles.