Tuning Polyacrylamide Precursor Viscoelasticity Using Nanoclay for Extrusion-Based 3D Printing of Hydrogels

Abstract

Polyacrylamide (PAM) hydrogels have shown great potential in applications such as tissue engineering, biosensing, and soft robotics due to their biocompatibility, low cost, and tunable properties. However, limited by the low viscosity and the relatively short chemical cross-linking time of the PAM precursor, direct 3D printing of PAM gel with desired mechanical properties remains challenging. This study addresses these challenges by incorporating Laponite nanoclay as a rheological/gelling regulator and nanofiller, alongside N, N′-methylenebisacrylamide (MBA) to accelerate curing. A combination of using Laponite nanoclay and MBA not only alters the viscoelastic characteristics of the precursor and the gelling time but also introduces a significant shear-thinning effect. The formulated PAM-Laponite mixture can be optimized to be adopted by conventional extrusion-based 3D printing to synthesize gel structures with good shape fidelity. The study also shows that the combination of nanoclay physical gelling, PAM chemical cross-linking, and the competitive molecular interactions among different gel compositions allows significant improvement and tunability in the mechanical performances of the resultant gel samples. Hereby, the work demonstrates an efficient and practical approach to tuning the rheological properties of the extrusion precursor for prototyping 3D gel structures suitable for biomedical applications.