Optimizing 3D Printing Procedure to Improve Aerosol Filter Fidelity

• John Thomas, Chemical Engineering, University of Delaware

• Catherine Fromen, Chemical and Biomolecular Engineering, University of Delaware

3D printed aerosol filters are a major component of the Total Inhaled Deposition in an Actuated Lung (TIDAL) Model developed by the Fromen Lab. These filters, consisting of Weaire-Phelan unit cells, can approximate lung geometry due to their densely packed structure. To ensure correct translation from computational models to the filters, the porosity of these prints are measured and compared to a calculated target porosity. The goal of this study is to determine a 3D printing procedure that generates filters with porosities similar to the computational files. The filters are printed using masked stereolithography (MSLA) with photopolymeric resin and then post-processed to remove excess resin from the filters. MSLA printing fidelity relies on multiple variables that must be optimized. This study aimed to optimize print fidelity through the following variables: print y-axis orientation, post-processing steps, and various print settings. Print orientation was determined to be the most significant factor in print fidelity, where 60 and 90 degree orientations performed the best. For post-processing, the analogous factors of shaking and sonicating the filters were found to be significant. It was found that the high counts of  sonication exposures yielded the best porosity. For the print settings optimization, the layer height setting and rest time before release setting were significant, with a print using the best levels for each yielding the highest recorded porosity. In addition, it was found that the variance in porosity for each printed triplicate decreased by an order of magnitude from the original optimized condition. Lastly, there was no significant print-to-print variation between prints with the best print settings. The procedure developed in this study can be applied to future TIDAL model iterations and optimize porosity for lattices of varying unit cell geometries and size.