Printability Evaluation of UV-Curable Aqueous Laponite/Urethane-Based PEG Inks

In the present research, we evaluated the printability of inks that were formulated using an acrylate-endcapped urethane-based poly(ethylene glycol) hydrogel precursor (AUP) and a silicate-based nanoclay Laponite. Flow characterization of the AUP/Laponite hydrogel inks revealed both yielding and shear thinning behavior, strongly dependent on the concentrations of the AUP and Laponite. In order to have a better insight into printability, the flow behavior along the cross section inside the printing needle was evaluated from the experimental shear flow data. The maximum stress values estimated inside the needle were applied to investigate the structural recovery of the inks using oscillatory rheology. Close analysis of the shear modulus recovery of the AUP/Laponite inks revealed a biexponential behavior, indicating a two-step recovery mechanism. The recovery mechanism is composed of fast and slow recovery steps and it appears that the shape fidelity after ink deposition is primarily controlled by the fast recovery contribution. Optimal printability was achieved for the ink formulation with the shortest characteristic time as well as a high modulus (>500 Pa) compared to the inks which could not be printed into well-defined structures. In the final part, cell interactivity of the three-dimensional (3D)-printed scaffolds was evaluated via live/dead cell assays.