Three-dimensional aerosol printing by enlarged, optimized and charged nanoparticles

The article explores the challenges and potential of creating micro-sized structures using metals and oxides with an aspect ratio of 1 in the field of printed electronics. Specifically, it focuses on the production of microstructures from loosely bonded metal particles with mean size from 30 to 80 nm. These conglomerates exhibit unique electrical and optical properties that differ from monolithic structures, making them a subject of special interest. The study introduces a system capable of producing porous microstructures on silicon substrates using spherical nanoparticles. This is achieved through a series of steps including synthesis, sintering, charging, and electrostatic focusing through a stainless steel ball grid array stencil. As a result, uniform Au microstructures each measuring approximately $25\mu m$ (through $280\mu m$ holes) are successfully printed across the entire surface of the stencil, which covers an area of about 0.7 cm${}^2$. Moreover, the potential applications are not limited to this achievement. Furthermore, the article provides experimental evidence supporting a hypothesis regarding the diffusion mechanism responsible for the broadening of the resulting structures. This mechanism is based on the theory of charge distribution among nanoparticles during the charging process in the corona discharge region. Additionally, the study demonstrates the deposition of nanoparticles made of Ag, ZnO and SnO${}_2$ oxides using the same method. The research presents the formation of an uncharacteristic pattern associated with this deposition method, where nanoparticles are deposited in a discrete manner rather than forming continuous structures. This finding adds to the understanding of the complex behavior of nanoparticles during the printing process and opens up new avenues for further investigation in the field of printed electronics.