Low Shrinkage Hydrogel Infusion Additive Manufacturing of Ceramics and Metals

Additive manufacturing has emerged as one of the most powerful manufacturing tools available today. In particular, vat photopolymerization (VP) techniques are especially promising as they are inexpensive, and capable of achieving high resolutions and throughputs. However, the fabrication of ceramics and metals materials with VP still poses many challenges — particle-filled photosensitive slurries are hard to use due to high viscosities and often have poor resolutions due to light scattering. Inorganic-organic photoresins are limited in their compositions and are often difficult to synthesize.<br/>We recently pioneered a method called hydrogel infusion additive manufacturing (HIAM) that circumvents some of these challenges. In HIAM, a metal-ion infused hydrogel is thermally treated to convert it into a metal oxide or metal. While a facile and versatile process, the conversion of the polymer into the ceramic/metal is often accompanied by a significant amount of shrinkage, often upwards of 60%. The large shrinkages observed limits the utility of this process.<br/>Here, we report the next generation of HIAM technology (HIAM Gen2) for the low-shrinkage fabrication of ceramics and metals. Using a series of intermediate processing steps, we show that we can increase the loading of the inorganic phase within the hydrogel by almost an order of magnitude. Accordingly, the linear shrinkage of ceramics made using this new HIAM Gen2 technology is now approximate 20%, 3x lower than the current state of the art. We anticipate that the chemistries and processing techniques developed in HIAM Gen2 will be broadly applicable to other gel-based polymer-derived material technologies, and enable the use of VP for the fabrication of ceramics and metals.