Fabrication of Micro Pillar Arrays Via Aerosol Jet Printing

Direct write printing is one of the evolving technologies that can be used to fabricate 3D structures such as ceramic micro-pillars. Direct write printing processes can print high resolution structures in the micron or sub-micron range. These structures find their applications in 3D Micro-Electro Mechanical Systems (MEMS), ultra-sound and thermal imaging, heat exchangers and solid oxide fuel cells. The present research is focused on fabrication of vertical ceramic micro-pillars using the Aerosol Jet direct write printing process for enhancing the aspect ratio of the pillars. Aerosol Jet printing offers flexibility with respect to ink compositions as compared with fabrication techniques such as lithography or ink-jet printing. This study includes an investigation of ink compositions to formulate a printable Yttria Stabilized Zirconia (YSZ) ink. YSZ ceramic is chosen due to its wide range of applications. The effect of solid loading fraction on the viscosity of ink is also studied. The study identifies significant printing process parameters and their relationships to the process output for printing high aspect ratio YSZ micro-pillars. An experimental approach is followed where the diameter and height of pillars are the response variables of interest. A screening experiment with fractional factorial model is conducted in order to obtain the levels of process parameters that resulted in pillars with diameters as small as 50 µm and heights up to 1000 µm. After finding suitable process parameter levels, experiments were conducted to identify the minimum distance between consecutive pillars. Once the minimum possible distance was identified, 4x4 pillar arrays were printed on YSZ substrate and sintered in order to achieve sufficient pillar strength. Pillars with average diameters as small as 50 µm and heights up to 1000µm were achieved through this process.