Rheological guidelines for vat polymerization printing of nanoparticle suspensions

Nanoparticle suspensions are traditionally difficult to print using vat polymerization techniques due to high viscosity, yield stress, and thixotropic behavior. Despite the growing interest in using nanoparticle suspensions, a notable gap exists in our understanding of the time-dependent structure development driven by these various rheological phenomena during printing. We hypothesize that the interplay between transient rheology and printing timescales defines successful and predictable printing. In this study, we address a model material system of silica nanoparticles suspended in a commercial 3D printing resin where viscosity, thixotropy, and yielding are well-controlled across a continuum of behavior. We aim to understand the rheological parameters that dictate the printing operation using in-situ photo-rheology. The model system offers a simplified platform to explore the transition from ideal Newtonian to complex non-Newtonian behavior in nanoparticle suspensions. Through systematic investigation of time-dependent rheology and its correlation with printability, we seek to elucidate the process effects on the mechanical properties of the printed structures.