Session: 16-01-01: Government Agency Student Poster Competition

Paper Number: 150193

150193 - Enhanced Resolution, Throughput, and Stability of Aerosol Jet Printing via in Line Heating 

Aerosol jet printing is a direct write, non-contact, additive manufacturing technique that is particularly suitable for flexible and conformal devices, rapid prototyping, and hybrid electronics which are not feasible using standard processes. This manufacturing method features micron-sized droplets (1-5 µm) which are produced through ultrasonic or pneumatic atomization. These droplets are subsequently transported to the printhead on a carrier gas. In the printhead, they are focused and accelerated by an annular sheath gas through a nozzle before impacting on the surface to create printed, high resolution features (10-100 µm). Despite these advantages, aerosol jet printing has experienced limited adoption in manufacturing environments due to low material throughput, instability, and complex process optimization. A significant challenge is the inherent tradeoff between line resolution and deposition rate which becomes especially problematic when operating in high throughput, solvent-rich regimes. When under a high velocity gas jet, the excess material on the surface can cause liquid phase spreading resulting in low resolution and poor line edge morphology. The research herein aims to reduce these barriers to implementation and provide greater insight on the fundamental mechanisms of the printing process by exploiting droplet evaporation in the aerosol phase. This simple intervention allows adjustment of print characteristics on the fly, including partially decoupling the deposition rate and resolution by reducing liquid phase spreading following impaction. This was implemented using a custom in line heating module to facilitate partial droplet evaporation prior to deposition. The in line evaporation technique was demonstrated with a variety of inks including colloidal dispersions in nonpolar organic solvents (silver nanoparticle), colloids with polymeric dispersants in polar organic solvents (conductive carbon), and water based polymer solutions (polyimide). Printed features were analyzed for resolution (line width), cross sectional area, and deposition rate using an optical profilometer. Image analysis implemented Gwyddion for baseline subtraction and a MatLab code for data processing. This method successfully reduced the liquid deposition rate without suppressing the solids deposition rate, yielding taller, narrower features with aspect ratios improving from 0.0025 to 0.1 between 30 °C and 80 °C. Heating the printhead to a modest 80 °C resulted in a 90% reduction in the sensitivity of resolution to changes in deposition rate, allowing higher throughput and improved consistency between prints. In line heating was demonstrated to be effective for a broad range of ink chemistries, illustrating this method’s versatility for aerosol jet printing. The ability to control droplet characteristics in flight provides a key operator control to broadly improve printing capabilities, including for high aspect ratio structures, conformal printing, and patterning on rough, insulating surfaces.  

Presenting Author: Bella Guyll Iowa State University

Presenting Author Biography: Bella Guyll is a third year PhD student at Iowa State University in mechanical engineering. In 2021 she was awarded the prestigious NSF GRFP fellowship. Her research interests include additive manufacturing and various printing methods. Specifically, she focuses on how the underlying fundamental mechanism of droplet evaporation in aerosol jet printing can be exploited to improve the throughput, reliability, and performance of the technology.

Authors:

Bella Guyll Iowa State University
Logan Petersen Iowa State University
Cary Pint Iowa State University
Ethan Secor Iowa State University