Direct Ink Writing (DIW) is an advanced additive manufacturing 3D-printing technique with significant potential for producing hydrogels in biomedical and engineering applications. This study presents a comprehensive rheological analysis of the yielding and recovery properties critical for ensuring the printability of carboxymethyl cellulose (CMC)-based hydrogels incorporating atenolol, an antihypertensive agent, as the active ingredient. The viscoelastic properties under shear conditions were examined using Large Amplitude Oscillatory Shear (LAOS) testing. To obtain both qualitative and quantitative insight into hydrogel dynamics, Lissajous-Bowditch plots and Fourier Transform (FT) coefficients were analyzed. The evaluation of stress signal anharmonicity and the decomposition of stress into its elastic and viscous components allowed for distinguishing structural evolution under flow among the tested hydrogels. Additionally, the analysis of the Sequence of Physical Processes (SPP) during each deformation cycle provided deeper insight into oscillatory yielding behavior, emphasizing the role of elastic strains in determining printability. Overall, the study offers valuable understanding of the nonlinear viscoelastic behavior of CMC-based hydrogels, providing a framework for optimizing hydrogel formulations in DIW applications.

Botikaz betetako hidrogelen 3D inprimaketa: erreologia-inprimatze baldintzen harremana produkzioaren informazio-fitxa

As a way of recycling epoxy thermoset materials, they were blended with polycaprolactone (PCL) and processed in the form of filament to be used for fused deposition modeling (FDM) 3D printing. Three different epoxy materials were considered: a lab‐cured epoxy resin, a lab‐cured epoxy/PCL blend, and a commercial epoxy composite containing fiberglass (FR4). These three thermosets were milled and mixed with pure PCL. The distribution of the epoxy in the PCL matrix was analyzed by Fourier Transform Infrared Spectroscopy (FTIR) coupled to a microscope. The filler FR4 and DGEBA were adequately distributed in the matrix. The rheological study anticipated good adhesion between the layers, without clogging at printing temperatures. The rheological model also predicted filament buckling. Because of that, external assistance (PLA) was required to obtain appropriate printed samples, avoiding buckling. The mechanical properties of the specimens were determined by tensile tests and compared with injection molded specimens. It was observed that the incorporation of the epoxy thermoset to the PCL matrix enhanced Young's modulus of PCL. Very similar results were obtained between 3D printed and injected samples. The proposed method could be of significant interest in employing thermoset epoxy waste as a cost‐effective reinforcement for fuse filament 3D printing materials.