Linking yield stress recovery to 3D printability across multiple particle-polymer mixtures, including the role of the additive polyethylene glycol

A fundamental challenge in direct ink writing (DIW) is identifying a quantitative rheological metric that robustly predicts 3D printability across diverse polymer/particle blends. By characterizing shear rate hysteresis through consecutive up- and down-ramps, we demonstrate that, under the rheological protocol employed in this study, a down-ramp yield stress exceeding approximately 30 Pa reliably predicts successful DIW printing of 20 mm-high slump cones. Beyond the polydimethylsiloxane matrices studied in earlier work, we systematically validate this framework across polyisoprene, polybutadiene, polyethylene glycol (PEG), and poly(ethylene glycol) diglycidyl ether, while expanding the dispersed phase beyond fumed silica to include carbon black and titania. The addition of oligomeric PEG was found to promote rapid thixotropic recovery of the down-ramp yield stress, thereby converting nonprintable suspensions into viable DIW inks for multiple polymer/particle combinations. Additionally, we address the impact of processing history, specifically mixing and degassing, on rheological reproducibility. These findings establish a predictive framework for DIW ink design rooted in the physics of yield stress recovery and demonstrate the transferability of this approach across a broad range of polymer-particle systems for additive manufacturing.