Enhanced aerosol jet printing: Leveraging jet visualization for increased stand-off distances

Aerosol jet printing (AJP) is a non-contact process capable of high-resolution (~10–100 μm) printing of functional materials on conformal and flexible surfaces, even at relatively higher stand-off distances (1–5 mm). However, it is not very clearly known how much the stand-off distance can be increased without losing focus of the jet. To date, printed patterns have been investigated to gain understanding of the printing process and to optimize the printing parameters, which may take a lot of effort for experiments as well as understanding of physics behind jet behavior. In this study, we proposed the use of a laser scattering technique to visualize the focused spray jet along the jet direction. The analysis of visualized scattering images facilitated the determination of both the aerosol beam's jet diameter and its breakdown length. By examining the breakdown length, we investigated the range of stand-off distances required for proper printing. This range was found to be significantly influenced by the turbulence of the free jet as it exited the nozzle. The research results revealed that an increase in either the mist flow rate or sheath flow rate leads to amplified turbulence in the jet, subsequently reducing the working distance of AJP. Conversely, an elevated atomizer flow rate leads to excessive aerosol generation which detrimentally impacts the jet by reducing its breakdown length, possibly due to the increased density of the mist flow. The research findings successfully demonstrate 3D surface printing with a stand-off distance exceeding 10 mm on a complex surface by optimizing the appropriate parameters.