3D Freeze Nano Printing for Multiscale, Multifunctional Porous Materials

Abstract

Hierarchical porous structures are ubiquitously around us (e.g., bamboo, wood, bone, bird wings). They exhibit many exceptional properties such as light weight, large surface area, and multi-functionality. It would be desirable to artificially replicate such bio-inspired structures. Depending on the specific material, the method to fabricate porous three-dimensional structure varies. Most of the basic idea is indirectly using a second-phase as template to replicate their porous structure. Among them, freeze casting is one that uses ice as template, thus, making it a versatile, low cost and environmentally friendly process. However, conventional freeze casting process can only fabricate porous objects with simple geometries such as cylinder, rectangle, based on the shape of the mold to hold the slurry or colloids. Additive manufacturing (AM), or three-dimensional (3D) printing, with the capability to fabricate a part directly from a computer aided design (CAD) model, can probably bridge this gap. Thus, this dissertation aims to investigate a novel fabrication approach to produce porous objects with arbitrary shapes based on the integration of disruptive 3D printing technology and freeze casting into one seamless freeze nano printing system. To this end, the research question is: can 3D printing be used to fabricate hierarchical, functional porous material? If yes, how to realize multiscale and multifunctional part fabrication? This research question is tentatively answered by the hypothesis: inkjet printing of aqueous nanomaterial integrating with ice templating followed by freeze drying process can fabricate 3D functional porous materials.