Numerical and experimental investigation of aerosol jet printing

A two-dimensional computational fluid dynamics model is presented to elucidate the fundamental aerodynamic phenomena dictating the morphology of aerosol jet printed features. Under compressible and laminar flow assumptions, governing equations were numerically solved to calculate crucial flow variables at discrete points throughout the fluid domain. Randomized single-factor numerical experiments were performed to unravel the role of volumetric flow rates of sheath gas, carrier gas, flow focusing ratio, overall gas flow rate, and aerosol droplet diameter. A Lagrangian discrete phase model was implemented to predict the trajectories of aerosol streams through the fluid domain at several process conditions. A mathematical model for predicting the width of the aerosol stream at the nozzle exit is also presented. Additionally, polydispersity in the droplet diameter distribution was modeled using the Rosin-Rammler distribution, and the role of the minimum droplet diameter in a polydisperse stream of aerosols in causing overspray is discussed. Overall, the numerical results showed good agreement with experimental measurements from an ultrasonic aerosol jet printing (AJP) system, making the computational framework a valuable tool for optimizing the printing process and for predicting the occurrence of printing defects.