We investigate the 3D-printing performance of hybrid hydrogels composed of gelatin and polyethylene glycol diacrylate (PEGDA). Printed gel structures are obtained by exploiting the thermoreversible gelation of gelatin to form self-supporting frameworks, which are subsequently stabilized through UV-induced crosslinking of PEGDA. Achieving reliable printing requires precise control of gelation kinetics. Direct cooling of the extruded material often results in filament heterogeneity and poor shape fidelity, while excessively fast gelation can lead to nozzle clogging. In addition, UV curing performed in air is hindered by oxygen inhibition, which reduces the efficiency of free-radical polymerization. To overcome these limitations, we implement an inverse quenching protocol on three gelatin/PEGDA hydrogel formulations with fixed PEGDA content (10 wt%) and increasing gelatin concentrations. By means of rheological measurements, we observe the formation of a metastable elastic state in which gelation kinetics are effectively arrested and the viscoelastic properties remain nearly constant over a time window suitable for extrusion. Furthermore, we demonstrate that the gel elasticity can be tuned over a broad range by controlling the thermal history and the sol formulation. This rheology-driven approach enables the identification of an operational processing window for extrusion-based 3D printing. When translated into the printing protocol, the method allows continuous filament deposition and the fabrication of three-dimensional structures with high shape fidelity.
Avallone et al. (Mon,) studied this question.