Lost Mold Rapid Infiltration Forming of Mesoscale Ceramics: Part 1, Fabrication

Abstract

Free-standing mesoscale (340 lm  30 lm  20 lm) bend bars with an aspect ratio over 15:1 and an edge resolution as fine as a single grain diameter (B400 nm) have been fabricated in large numbers on refractory ceramic substrates by combining a novel powder processing approach with photoresist molds and an innovative lost-mold thermal process. The colloid and interfacial chemistry of the nanoscale zirconia particulates has been modeled and used to prepare highly concentrated suspensions. Engineering solutions to challenges in mold fabrication and casting have yielded free-standing, crack-free parts. Molds are fabricated using high-aspect-ratio photoresist on ceramic substrates. Green parts are formed using a rapid infiltration method that exploits the shear thinning behavior of the highly concentrated ceramic suspension in combination with gelcasting. The mold is thermally decomposed and the parts are sintered in place on the ceramic substrate. Chemically aided attrition milling disperses and concentrates the as-received 3Y-TZP powder to produce a dense, fine-grained sintered microstructure. Initial three-point bend strength data are comparable to that of conventional zirconia; however, geometric irregularities (e.g., trapezoidal cross sections) are present in this first generation and are discussed with respect to the distribution of bend strength.

Lost Mold‐Rapid Infiltration Forming of Mesoscale Ceramics: Part 2, Geometry and Strength Improvements

“…The strength of the Gen1 material with trapezoidal cross section, dishing, and warping was reported previously 7. The mechanical strengths of the Gen2 material with rectangular and nontrapezoidal cross sections but with dishing and warping present and the Gen3 material with a rectangular cross section, minimal dishing, and minimal warping are reported in this study.…”

“…Ceramics, particularly yttria-tetragonal zirconia polycrystals (Y-TZP), have the high fracture strength and elastic modulus required for mesoscale surgical instruments 5. In the first part of this series on mesoscale (i.e., sub-millimeter) manufacturing, we reported a new microfabrication approach based on Y-TZP nanoparticulate processing, lost mold-rapid infiltration forming (LM-RIF) 7. The generation 1 (Gen1) mechanical test bend bars had a relatively high aspect ratio (15:1) and high resolution edges (<1 μm), and were manufactured in large numbers on refractory substrates (up to 200 000 bend bars per 10 cm × 10 cm refractory substrate).…”

“…The LM-RIF process is described in detail in Part 1 of this series 7. LM-RIF processing is an integration between semiconductor manufacturing based on ultraviolet (UV)-photolithography and ceramic powder processing first pioneered by Gauckler and colleagues, who patterned ceramic colloids on substrates 10–13.…”

3D Printing of Personalized Artificial Bone Scaffolds

“…47 Using this technique, a mold, which could be personalized with imaging and computer modeling and design, is fabricated with a desired porosity and geometry. This mold could be cast with the calcium phophosilicate suspension discussed above incorporating the desired optimized nanotopography.…”

A photopatternable superparamagnetic nanocomposite: Material characterization and fabrication of microstructures

“…It is known that bare SU-8 structures can exhibit a negative slope as well because of the absorption of deep UV light in the upper layer. Using a UV-filter to remove the sub-365 nm light could help reduce the effect of the negative slope [32,33].…”