A Rheological Study of Matrix Materials Used in Embedded Three-Dimensional Printing

Abstract

Embedded three-dimensional (EMB3D) printing is an emerging technique that is enabling the fabrication of highly complex, heterogeneous materials systems requiring intricate architectures. EMB3D printing involves the direct patterning of materials within soft supporting matrix materials via a translating print nozzle directed by pre-defined tool paths. To decrease the minimum feature sizes and general complexity that can be achieved with EMB3D printing, it is crucial to understand how the EMB3D printing matrix materials’ rheological properties influence their performance and behavior during the printing process. We have examined how thixotropic, fumed silica-filled polydimethylsiloxane-based matrix materials used in EMB3D printing are disturbed and yielded by translating nozzles during printing using rheological analysis and particle image velocimetry. Specifically we investigate how print speed (the velocity of a translating print nozzle), nozzle diameter, fumed silica concentration, and nozzle acceleration influence the region of yielding around a trans-lating EMB3D printing nozzle. By characterizing the velocity fields and analyzing the dimensions of the yielded regions, we determine that simple scaling relationships exist between these dimensions and both the matrix materials rheological properties and printing parameters through the use of nondimensional numbers, including the Oldroyd (Od) and Deborah (De) numbers. This fundamental knowledge will allow for great advancements of a highly applied technique.