Direct Ink Writing of Polymeric Materials for Advanced Applications
Abstract
3D printing (3DP) has gained interest in recent decades for forming custom structures with complex geometries which are not readily produced by traditional manufacturing techniques. This advance in manufacturing processes must coincide with the development of appropriate materials. This dissertation focuses on the design of high-performance materials for the extrusion-based 3DP method of direct ink writing (DIW). Feedstock inks for DIW must be viscous, shear-thinning, and thixotropic to hold their shape after extrusion and solidify into monolithic structures. To achieve these rheological requirements, two approaches were taken: 1) liquidous polymers were combined with a variety of particle fillers to produce paste-like composites and 2) mild heat treatment facilitated the gelation of a polymer sol to create a printable ink.
Through the above approaches, a library of inks spanning thermal energy regulation, tunable porosity, hybrid solid-liquid structures, and ultralightweight thermal insulators have been developed. The rheology, microstructure, mechanical properties, and end use performance of these inks were evaluated, and the printed objects were found to be effective at their target tasks. For example, the thermal energy regulating ink maintained a 40% lower temperature than the internal environment when heated. The porous materials had controllable mechanical properties, with elastic moduli ranging from 3.4 to 25.4 MPa depending on the porosity level. Fluid-containing structures had tunable microstructures, thus providing a modular platform for incorporating functional liquids into monolithic printed parts. Finally, printed ultralightweight polyimide aerogels possessed similar low densities, high surface areas, and thermal insulation capabilities to traditional cast aerogels, demonstrating potential use as bespoke thermal insulators for electronics on air and spacecraft. This library of materials paired with future directions in ink standardization will propel the approachable technique of DIW into advanced applications.
Description
Keywords
3D printing, direct ink writing, polymers, phase change materials, porous materials, hybrid structures, aerogels